MTN False sale and hard to get out of it

Was sold a contract with false advertising by telemarketer that claimed high internet speeds at low price, when device arrived it was far from what was described.

I cancelled the contract the following day after I assessed within the said cooling period, after a long back and forth of emails , finally cancelled the contract with their said Agent Mondo. Now MTN has been forcefully trying to debit my account for cancellation fees, now even threatens with listing on the bureau. I have been in contact with Mondo since the 7th of this month, Mondo is in agreement apparently sending requests to waiver the amount at MTN with no success. Everytime I call, I'm told it's been escalated. And MTN customer care is totally useless, nightmare to gain access to speak to one of the consultants

My reference case is: SR#***.

Terrible experience, beware of telemarketers.