Conned by Mtn retentions department

I have 2 contracts with mtn, 1 came to date of expiry. 2 days after I called the mtn customer care line to cancel my subscription because they asked me to pay an inflated amount. The customer care adviser was very deceptive and told me if I upgraded the penalty will be waived. To my surprise 1 month later my bill was over R3000. I come to realise it was a Ignition call center agent that was affiliated to mtn. When you call the retention department, calls are diverted to ignition. The call centre agent cut the call a few times so that the previous recordings will skewed. Im a client of over 25 years . Disappointed with mtn.