Complaints about the contract I took with MTN

MTN ****med me a lot and I would never take or recommend someone to take a contract with them again. I took a contract with them, I was supposed to get 10 GB anytime and 10 GB night data but they never gave me that data, I called and emailed them but no luck, they continued to debit the amount for the whole 2 years, even after the agreed 24 months they continued to debit until I called and cancelled the contract but still the continued to debit on my account until I decided to despute the debit order then they handed my account to their legal team without informing me, despite of me cancelling the contract with them. Now my name is tarnished and it is affecting my credit score. The worse nightmare I've never experienced.