MTN contracts

I recently app**** for a cellphone contract on the MTN online store, told I didn't qualify but two months got a call telling me I was approved for the phone I had app**** for. Got a call again informing of no stock for the particular gadget, fast forward I receive another stating the have the phone and want to deliver. once i got the phone I was displeased with the gadget as it overheated and the battery would not last more the 6 hours, I went to a MTN store to request the contract to be cancelled only to realize that the phone production was stopped due to the mentioned complications. I'm being still charged whilst I have returned back the phone and being asked to pay a cancellation fee of a phone that was not in my possession for more than 3 months. I'm totally disappointed at the way business is being run, please intervene as this is damaging to my credit score.