Rewardsco and Mtn are robbing Us

On 2020-11-11 I recieved a call from Rewardsco saying they are phoning on behalf of Mtn as my contract was due for upgrade. Indeed we agree on upgrading.I recieved the delivery on 11-12-2020 and notivced that the cellphones was 2019 model n not what I was looking for. On 14-12-2020 I returns the parcel n was told to wait for 14 days for my contract to be cancelled. Until today 03-03-2021 the contract is not cancelled.I established that I was issued with new contract instead of upgrading. I phoned Mtn and they told me that I must phone Rewardsco.Mind to phone Rewardsco you must wait on the line for more than 20 minutes before you get an answer.I phone them several times without any success. I am paying what I dont own now. Mtn dont want intervene. I dont know how much I spend on phoning them.