Bad service

I have received a call from Absa vehicle asset yesterday . I was contacted the reason why they called me was that my account was in arrears. I asked the lady how and was promised an apology letter by their manager .On Friday I had received a collection call again and I further ask the agent if they are smoking and he said I am telling him **** . I had paid the instalment prior month end . Now I get collection calls . I need to know why. My id number is 720 ********** 081