DISGUSTING SERVICE

So i cancelled my contract wth MTN after paying off everything effective April 2022. I subsequently ported my number to TELKOM due to their bad service and lack of concern for their customers and the abuse i suffered when trying to backlist my phone that was ******. So soon after the port, i started receiving sms that owe them. What i dont understand is how do i owe them and how was i allowed to port if i owe. I have been trying to engage them on twitter for almost two months and still no resolution. I dont know maybe if they mining this investigation because i dont get why it should take so long for someone to go into their system and check whats happened on my contract. They so ***********, everyday you deal with someone new and they tell you that someone will revert back. Its been 2 months now. I have never seen such high level of incompetency. Can someone get back to me and actually explain why they say i owe. I will be taking this further and lodging a complaint with a third party.