Still being charge for a cancelled contract

<p>On the 25th April we returned the Samsung S6 Edge that was 3 months into the contract. This was on the recomendation from MTN retions that they could do nothing about the signal in our area. They gave us a letter saying the contract should be cancelled and migrated to prepaid with no penalty costs. We handed in the phone to Yvonne Moswana. Apparently up to this date the phone hasn't been returned and MTN cannot process the cancelation. MTN are still charging me and for some reason they double debited this month!! I need this contract cancelled and must be refunded from the date of the phone being handed in!!</p>