Salary deduction on settled account

I e-mailed nsfas in November 2020 requesting a settlement amount on my loan. I received a response after 3 months. I paid the requested amount before the end of March 2021. I then requested a letter confirming that the account has been settled. The confirmation letter I received mid May.

However, they are still deducting from my salary and it is impossible to get through to them it's as if they are non-existant. Please help me out of this mysery.