********** upgrade on my existing MTN contract

I have taken out a 24 month contract with MTN in 2013 the contract was a laptop with which i received 1Gig of data monthly. last year (2015) the contract came to an end and i did not have it upgraded nor cancelled, so i continued to receive the Gig of data monthly. i then noticed the debit order suddenly increase,i then went into MTN at cape town international airport to enquire they informed me that the contract was upgraded in a store in Durban, they said we need to get an affidavit to state that i did not upgrade the contract, at the police station they informed me that i cannot get an affidavit but instead i need to open a case, i did so and they gave me a case number, it has been a couple of weeks now and MTN is still debiting my account for a cell phone contract that does not belong to me. Nobody has bothered to contact me regarding this matter even though i personally visited your branch at the airport to inform them about this matter. how is it even possible to have an upgrade going through on my name without my ID,i was advised in the store that the package upgraded was for an i-phone 5, it was done in December last year and i have been paying for this device since then.