Poor service

I am unhappy with the service I received from Mbd. My vodacom account was handed over to them (not sure of the date)then I called and requested for a settlement letter in Sept 2021 which was then emailed to me, after receiving it I made the payment of r3717.55 as was stated in the letter.Then Nov 2021 I called to request for the paid up letter and I was told I still owe an amount of r5.00 which on the 3rd of Nov 2021 I made the payment of r6.00 to cover it up. From there on I have been calling their offices trying to request for the paid up letter but have been told numerius times that it will be sent up until now I have not received the letter or any communication as to why I'm not receiving the letter.