threatening calls from your institution

Good Day

Please note that I'm been accused of owing DCC an amount of R26 000+ for my son in which we only registered and paid the 1st monthly payment, he then attended classes for less than months. I been receiving calls to make arrangements to pay the R26000.00 in which I do not see how I'm liable this money. Someone from your institution requested we send the affidavit in which we did, but yet I still receive threatening calls.

Kindly assist.