Sim card contract theft

Mondo sold me a sim card contract from MTN the sim card was then delivered to me on the following address : 352 apartment on Oak avenue , The above mentioned sim card was not never worked because the sim card was not registered for rica , I then requested a cancelation from mondo since the sim card never worked of which they did not assist .

I was then forced to pay the amount of R969 for my account because my account was in arrears of which i did because this was affecting my credit record . I reached out to MTN for them to cancel the contract because i cant pay for something that is in active , Mtn then told me that its not their jurististiction to cancel this contract since it was taken with Mondo but however Mondo also don't want to cancel the contract .