Worst company ever!!!!

I received a call from them in Jan 2019 that I have an hospital account outstanding. I did not know about the account and I paid it, also sent thru the proof of payment. It is 28-06-2019 and they are still sending me E-mails and SMS's about the account being over due. The service is terrible and the people working there is ***********!!!! I have never dealt with such arrogant people. Every time I phone to resolve the issue the manager is on lunch or in a meeting or anywhere except doing their wor****!!!!!! Their excuse is that "someone" did not update the proof of payment