100% bad customer service from MTN

I am so tired to MTN taking me from pillar to post and their consultant giving me wrong information. I have closed my wifi contract sometime early this year now when I need a PAID UP LETTER am being made a fool by multiple people on call. Why is it so hard for them to just give me my PAID UP LETTER since I don't owe them anything? Am so tired an exhausted about this whole situation. I was not even handed over ,I just settled my outstanding amount and closed the contract but now I have anxiety because of this. ALL I NEED IS A PAID UP LETTER for heaven sake!!!!