Well, that may depend on your ethnic heritage or the country you live in to some degree. Because it is possible for more than one person to come up with the same idea in roughly the same moment in time, there could have been more than one inventor of the telephone.
Although Alexander Graham Bell is considered the inventor of the telephone in the USA, Canada, and Scotland, other countries that had no historical affiliation with him tend to look for possible inventors of their own ethnic background or their own country as THE inventor of the telephone. Much has been written to address this never-ending debate and it is doubtful that there is any way of proving who really came up with the idea and put it into practice first. Even in the USA, many court battles were fought between Bell and several challengers to his right to be called the inventor of the telephone.
The following is from a book titled "The History of the Telephone" by Herbert N. Casson - First edition - A. C. McClurg & Co., Chicago - Published: 1910. The following paragraphs from the book give an account of some of the court battles that Bell went through in defending his claim as the inventor of the telephone:
"After Gray, the weightiest challenger who came against Bell was Professor Amos E. Dolbear, of Tufts College. He, like Gray, had written a letter of applause to Bell in 1877. "I congratulate you, sir," he said, "upon your very great invention, and I hope to see it supplant all forms of existing telegraphs, and that you will be successful in obtaining the wealth and honour which is your due." But one year later, Dolbear came to view with an opposition telephone. It was not an imitation of Bell's, he insisted, but an improvement upon an electrical device made by a German named Philip Reis, in 1861.
Thus there appeared upon the scene the so-called "Reis telephone," which was not a telephone at all, in any practical sense, but which served well enough for nine years or more as a weapon to use against the Bell patents. Poor Philip Reis himself, the son of a baker in Frankfort, Germany, had hoped to make a telephone, but he had failed. His machine was operated by a "make-and-break" current, and so could not carry the infinitely delicate vibrations made by the human voice. It could transmit the pitch of a sound, but not the QUALITY. At its best, it could carry a tune, but never at any time a spoken sentence. Reis, in his later years, realised that his machine could never be used for the transmission of conversation; and in a letter to a friend he tells of a code of signals that he has invented.
Bell had once, during his three years of experimenting, made a Reis machine, although at that time he had not seen one. But he soon threw it aside, as of no practical value. As a teacher of acoustics, Bell knew that the one indispensable requirement of a telephone is that it shall transmit the WHOLE of a sound, and not merely the pitch of it. Such scientists as Lord Kelvin, Joseph Henry, and Edison had seen the little Reis instrument years before Bell invented the telephone; but they regarded it as a mere musical toy. It was "not in any sense a speaking telephone," said Lord Kelvin. And Edison, when trying to put the Reis machine in the most favourable light, admitted humorously that when he used a Reis transmitter he generally "knew what was coming; and knowing what was coming, even a Reis transmitter, pure and simple, reproduces sounds which seem almost like that which was being transmitted; but when the man at the other end did not know what was coming, it was very seldom that any word was recognised."
In the course of the Dolbear lawsuit, a Reis machine was brought into court, and created much amusement. It was able to squeak, but not to speak. Experts and professors wrestled with it in vain. It refused to transmit one intelligible sentence. "It CAN speak, but it WON'T," explained one of Dolbear's lawyers. It is now generally known that while a Reis machine, when clogged and out of order, would transmit a word or two in an imperfect way, it was built on wrong lines. It was no more a telephone than a wagon is a sleigh, even though it is possible to chain the wheels and make them slide for a foot or two.
Said Judge Lowell, in rendering his famous decision:
"A century of Reis would never have produced a speaking telephone by mere improvement of construction. It was left for Bell to discover that the failure was due not to workmanship but to the principle which was adopted as the basis of what had to be done. Bell discovered a new art--that of transmitting speech by electricity, and his claim is not as broad as his invention. To follow Reis is to fail; but to follow Bell is to succeed."
After the victory over Dolbear, the Bell stock went soaring skywards; and the higher it went, the greater were the number of infringers and blowers of stock bubbles. To bait the Bell Company became almost a national sport. Any sort of claimant, with any sort of wild tale of prior invention, could find a speculator to support him. On they came, a motley array, "some in rags, some on nags, and some in velvet gowns." One of them claimed to have done wonders with an iron hoop and a file in 1867; a second had a marvellous table with glass legs; a third swore that he had made a telephone in 1860, but did not know what it was until he saw Bell's patent; and a fourth told a vivid story of having heard a bullfrog croak via a telegraph wire which was strung into a certain cellar in Racine, in 1851.
This comic opera phase came to a head in the famous Drawbaugh case, which lasted for nearly four years, and filled ten thousand pages with its evidence. Having failed on Reis, the German, the opponents of Bell now brought forward an American inventor named Daniel Drawbaugh, and opened up a noisy newspaper campaign. To secure public sympathy for Drawbaugh, it was said that he had invented a complete telephone and switchboard before 1876, but was in such "utter and abject poverty" that he could not get himself a patent. Five hundred witnesses were examined; and such a general turmoil was aroused that the Bell lawyers were compelled to take the attack seriously, and to fight back with every pound of ammunition they possessed.
The fact about Drawbaugh is that he was a mechanic in a country village near Harrisburg, Pennsylvania. He was ingenious but not inventive; and loved to display his mechanical skill before the farmers and villagers. He was a subscriber to The Scientific American; and it had become the fixed habit of his life to copy other people's inventions and exhibit them as his own. He was a trailer of inventors. More than forty instances of this imitative habit were shown at the trial, and he was severely scored by the judge, who accused him of "deliberately falsifying the facts." His ruling passion of imitation, apparently, was not diminished by the loss of his telephone claims, as he came to public view again in 1903 as a trailer of Marconi.
Drawbaugh's defeat sent the Bell stock up once more, and brought on a Xerxes' army of opposition which called itself the "Overland Company" Having learned that no one claimant could beat Bell in the courts, this company massed the losers together and came forward with a scrap-basket full of patents. Several powerful capitalists undertook to pay the expenses of this adventure. Wires were strung; stock was sold; and the enterprise looked for a time so genuine that when the Bell lawyers asked for an injunction against it, they were refused. This was as hard a blow as the Bell people received in their eleven years of litigation; and the Bell stock tumbled thirty-five points in a few days. Infringing companies sprang up like gourds in the night. And all went merrily with the promoters until the Overland Company was thrown out of court, as having no evidence, except "the refuse and dregs of former cases-the heel-taps found in the glasses at the end of the frolic."
But even after this defeat for the claimants, the frolic was not wholly ended. They next planned to get through politics what they could not get through law; they induced the Government to bring suit for the annulment of the Bell patents. It was a bold and desperate move, and enabled the promoters of paper companies to sell stock for several years longer. The whole dispute was re-opened, from Gray to Drawbaugh. Every battle was re-fought; and in the end, of course, the Government officials learned that they were being used to pull telephone chestnuts out of the fire. The case was allowed to die a natural death, and was informally dropped in 1896.
In all, the Bell Company fought out thirteen lawsuits that were of national interest, and five that were carried to the Supreme Court in Washington. It fought out five hundred and eighty-seven other lawsuits of various natures; and with the exception of two trivial contract suits, IT NEVER LOST A CASE."