NSFAS paid in full but still harasses you!

Not only did I successfully pay my account with NSFAS in full, I overpaid them due to misinformation on their part. I even had to send through proof of payments numerous times to their manager who never once acknowledged receipt. Only 3 months later did they send me a reimbur*****t form. Then, to top it all off, I started receiving threatening sms's and phone calls claiming that I still owed the full amount, 9 months after overpaying the account!