Phone call charges!

Foschini has been hounding for a R50 - yes R50 outstanding amount on my installment. I have been paying a substantial amount every month but due to the useless postal service was unaware that my installment has increased. After receiving an sms I called the head office and was told everything would be fine once I paid. Sorted - NO! I was then harassed almost daily requesting this R50! When I got my emailed account for the first time a few days ago I was astounded to see that I had been charged for a phone call and a letter - which up until now I have not received - see previous postal service comment. So, Foschini is expecting me to pay their phone bill and letter service! Surely then they should pay for the call I made to them! I am disgusted that they would treat a diligent customer this way. I shall be paying off my account and then closing it. Truworths, Edgars and Woolworths are welcome to my money from now onwards.