Pathetic

I had a loan with Sanlam loans in 2016.I called them and requested a settlement amount as I wanted yo pay it off. They emailed me the letter and told me it was valid for 5 working days. I then paid off the amount the same day which was around the 22nd of Sep.On the 20th of Oct which is my payday I was surprised to see a debit order from Sanlam. When I called them they said I didn't pay on time,I then send them proof of payment which showed the exact date that I paid and they said they will rectify.Now I have to keep calling them so they can refund my money.I feel their service is pathetic and I dont wanna deal with them ever again in my life.