MTN (SSDA) UNPROFESSIONALISM

I paid off their account in July through SSDA, requested the paid-up letter which I still have not received. I'm still receiving emails from their lawyers (SSDA) to settle the very same contract account I paid off three months ago. What version of a system that doesn't show and update if a person has paid? When will I get my paid-up letter as proof of a closed account?

These people are very unprofessional, I regret associating myself with them.