MONEY DUE TO ME

I had a personal loan with FASTA and I over payed. I found out about this days ago that I have an amount that is due to me. I have raised this with them but they have not responded or paid back my money back into my account. I believe they were supposed to inform me and pay back the money back. I have run out of patience, and the part that's making me this impatient is the fact that I had to find this out myself, they're keeping quiet