Account upgrade

Upgraded my phone last year March. Received a call last week informing me i need to upgrade. Told caller i was not interested and in actual fact it is not possible since my contract is only a year into a two year period. This past weekend my phones Internet services was suddenly disconnected and i received \ thank you for upgrading \" messages from Mtn. Upon contacting them i was informed that i upgraded my contract at some building which they couldn't even give a location for. I informed them that wasn't possible since i didn't and they need to rectify my contract or i will stop it. I was informed i need to send a affidavit and a proof of my id to them and if i fail to do so and stop my contract, legal action will follow. How can they upgrade without proof of id, address and my signature."