difficulties of cancelling my cellphone contract

I took a contract cellphone contract Redmi 10A with a total value of R1888 with a hope of strengthening mi credit score....but that dream was faced away by Mondo sales consultant who gave me mega flex air time of R370 i didnt agreed to....the monthly instalment of a phone was R50 and R10 for insurance, R98 data...but instead the amount grew to 520 per month after being given that airtime by force and even worse i have not being using the airtime i threw away the sim cz i had one number that i was already using and even now they are depositing the airtime with a hope of burying m with a huge debr....now i want to cancell the contract the cancelliation team keeps on giving m unreasonable amount like R5000 cancelliation fee...i was willing to pay of my account but they are make it difficult for me cause am not earning that much so now my credit score is turnished i wouldn't advice any1 to take up a cellphone contract with these people they are ****** who take from the poor out of greed