No communication

I had a loan account with Fnb which I settled. I then tried to contact the Personal loan department to stop the debit order, but after holding on for 20 minutes, I got disconnected. This happened twice. The debit order then went of my account. I tried to contact them again via telephone, but with no luck. I then emailed them twice also with no reply. I then contacted my branch manager in Stellenbosch, Shaun, but he too did not respond. According to my accountant, they have to refund debit order and also for interest over charged.