ABSA vehicle finance abuse

I always pay my account on time! Today I have been hounded by absa vehicle finance from 8.00am till now 15.59. I always pay my account the 28th and like this month I paid as per normal on the 28th! Less than 24hrs later I am been harassed via sms and now calls for their call centre asking me about my payment which I made! What kind on treatment is this especially when I paid my account! Now the agent is still on the call refusing to hang up because I want to complain! Have been holding for now 14 min