Paying for a contract I don't have

This is honestly the last place I wanted to revert to, but it has been 3 months and it seems I have no choice.

In October 2020 I received a call from a "MTN" sales person to upgrade my contract. What was sold to me and what i received was a lie. I specifically said I need a dual sim phone, Only to find out after delivery, MTN doesn't support dual sims, and I can return the phone to any MTN store, which i did the next day. Then the problems started.

I was told by the MTN store to phone the agent after 24 hours with a IRM number. Did that, they said the cancellation will take up to 8 weeks. After 8 weeks i followed up, NO ONE can help me. I made numerous calls and still waiting. Some time in this process I received a RC number as well.

I phoned 3 weeks ago and the agent told me my cancellation was finally submitted and should wait for an sms that will be sent to me within a few days. NO sms after 2 weeks. Last week Monday (18 Jan 2021) Chatted to someone via the instant chat, and that person said i would receive an sms within 5 days. (still no sms). Immediately after the chat i received an SMS saying "Please note that MTN's new system does not have the function to cancel/reverse an upgrade". I have spoken to over 20 people and absolutely no one has ever mentioned that they don't do cancellations.

It's been 3 Months, I have paid for this contract every month! I need it cancelled ASAP and reimbursed!