Phone contact list keeps deleting tel numbers, addresses, duplicates names, etc. Pulls in incorrect info perhaps from Facebook or somewhere.

My iPhone 6 s Plus telephone contact list keeps changing. It deletes telephone numbers and addresses I personally input. It duplicates names (showing all email addresses people ever used even if not current), It keeps the names I input, email addresses, and now has a FaceTime line I don't remember seeing before. I have tried to edit the revised contact list with the correct information but it keeps changing back. Went to Verizon Store about problem but they were stumped. Note this problem started with my iPhone 5 and carried over to my new phone. Help.