Faulty Phone

I took a contract on a Sony M5 with Cell C, within a week the phone started giving me problems. I contacted Cell C and they advised they were going to send someone to collect the phone from me. But because they were taking too long, i took the phone back to the Cell C head Office myself. they advised that all their Sony M5 phones were faulty and that they wer going to cancel my contract and I wouldnt have to pay. Now they debited my account, and when i call Cell C they keep on transfering me from pillar to post. Why does Cell C expect me to pay for a phone i do not even have, they are the ones that gave me a faulty phone but now expect me to pay for it?