I feel ******

Omw I am so upset with NSFAS as last year in November 2017 they advised me on an invoice that from 01/10/2013 my amount owing was R52082. 82 Interest earned till date effective 20/11/2017 was R10 971 so I figured that for 5 years the interest is about R11 000 estimated, now in March the figures drastically changed, I had paid 4 * R1000=R4000 over 4 months and effective March 2014 I got a new statement saying that my interest as increased from R10 971 to R12000 how is this possible for 3 months that my interest goes up for nearly R2000 nobody can give me an answer amantle was the manager who was so unprofessional he didn't reply to my calls or emails for days. They kept saying they are going to call but I had to call several times and then amantle couldn't answer my questions. I feel ****** as you'll can't give me a set answer