The question of who invented the telephone in not be the name of a single person. Many of the debates around who invented the telephone involve the names of Antonio Meucci, Elisha Gray and Alexander Graham. But in recent years I have also discovered the work of Dr. David Alter who was also a pioneer in telephone technology.
Check out the answers below for a bit more details on the evolution of the telephone.
https://www.quora.com/Who-invented-the-telephone/answer/Tom-Peracchio
https://www.quora.com/When-was-the-very-first-telephone-created