Angry customer mtn useless

Your service is appalling we took a contract on April 2023 i had another contract that was coming to an end in August 2023 i got a call from Rewards Co who MTn is telling me is a third party company they had asked me to upgrade obviously didn't want to as i had just taken new phones but you guys went ahead and canceled my latest contract and asking for us to pay over R11000. All this is happening to something i did not agree to i want my contract to be reinstated so that i can continue with my installment. I have went to the MTN store they telling me they can't help us as rewards co is a third party company but how did they get my information also why would i want to upgrade a contract if i have just taken a new one also the upgrade contract you say i agreed to where are the new phones