Contract upgraded without my consent

I had a Vodafone smart tab contract from 2015 and I was paying R80 every months with 500MB data. the contract ended in october and to my suprise vodacom deducted R1287 from my account the following months. when I went to enquire I found that the contract had been upgraded and someone took an iphone8 under my name without any phone call or any communication from vodacom I didnt even recieve an offer to . They told me to report it as ***** and said I must send emails and signatures to prove that I didn't upgrade the contract. I did all that and still waiting for a response. I keep on calling vodacom, going to the stores and no one is able to assist me. and my credit score is the one being affected.