MTN frustration

I took out an MTN online contract with Mondo in December 2023. I received the wrong color and notified MTN immediately. I was told to go to a direct store which was 154,4 km away. I returned the phone the following day and received an RMI number and I was advised to call 135 for a cancellation. A few months later I went to the MTN store at the Checkers Center in Welkom, where I was assisted by Nico. He advised to have sent an email on my behalf requesting a cancellation and refund as it wasn't done before. I have been billed since December to date. I recently went to my bank to cancel the debit order seeing that I'm still being harassed with debit order reminders of something I requested cancellation for a long time ago. Today I called 135 and was transferred to 136 and many other departments. Every consultant that I was being transferred to kept apologising instead of helping me. They kept telling me how they can't assist and transferred me over and over again. I'm frustrated 😤 from being sent from pillar to post. I also had an issue with the month to month router that I'd pay and it wouldn't work. I returned it to the store and today when I called 135 I was told it was still in transit and it couldn't be cancelled. This was returned to the store more than a month ago. MTN has failed me dismally to a point that if I had enough money, I would sue them.