***** ON MY ACCOUNT-3 phones taken without my knowledge

Someone took 3 phones under my MTN contract. My details were changed on their database,ie, address; gender. I only realised when a debit order was taken from my account. Now they keep billing me even though I have reported the case in January. Their collections department even calls me for me to pay for phones that I never signed for. Their system is not safe at all be warned.