MBD customer service is horrible

MBD is a **** and I seriously don't know why homechoice still uses them as a collector.i called in some time in February to request for a settlement figure,they gave it to me and sent me a link to make payment,their link was not working so I made payment on the home choice app,settling my account. 2 weeks later I get calls saying I'm owing them R500,I've been calling them this entire week requesting a settlement letter so I can get them off my back,I still haven't received it,all they do is harass us with text messages and when we request for something in writing so to refer to same after payment and just in case they come back again and say payment was not sufficient. I am helpless and tired,why would you bother working with collections if you not going to provide the service properly?your managers are ****s,they confirm telephonically that we can pay a certain amount only to come back and say no,that's not enough knowing we have nothing to refer to