Cancellation of contract

I opened up a WiFi contract with MTN last year in January at it was only for a year. I requested for cancellation upon the ending of the contract which was on the 31st of December as that was the only time they said I could submit it without being charged for early cancellation. They told me cancellation takes 3-4 days and I don’t have to pay. I started receiving emails that I am owing cause the debit order did not go through I have been calling MTN since the 6th of January 2025 and no one is giving me a straightforward answer as to what’s the way forward, I am concerned with this affecting my credit score I haven’t even received confirmation that the contract has been cancelled. I asked to speak to a manager no one has called back or responded, I always have to follow up with them to get a response and when I do there hasn’t been an update on anything.