Mischievious Behaviour

I took a WIFI last year cant remember the month. Fast forward this year I emailed them because I wanted to cancel it, was advised that I take take it to the branch near me. I went to the Southgate branch on the 1st of June 2024 to return it, I filled all the necessary docs. I did not get a reference number for the return however I got a message that they will collect from the store. Ever since that day every month am still getting emails to say I must pay. Went back to the branch again the consultant said I must ask the consultant that helped in June to give me a reference number so I can escalate on my end, I waited for the him but he left me standing in the store. I have then escalated my matter to their customer care and shared my story but they cant help me without the reference number. Cant they check the reference number on their end? I mean they have my ID copy they sure can find all that information on their system. This is ridiculous I dont have the time to go back to the branch and beg for something that was supposed to be given to me on that day but was not given. MTN better do something with this and all the complaints they are getting.