Unpleasant service

I had an outstanding amount of R536 in October 2018. December the 1st I sent someone money to pay for me. And they picked up Paul something not me and the account was paid up and I was not able to pay. I went twice personally to diffrent stores few days after, the 1st one the lady made copy of my ID and the slip showing the wrong account details and said ***** department will contact me and it never happend and by then the amount has gone up by R269. Who is suppose to pay for that because it was thier system that I was unable to pay the actual amount on time.. Can you please rectify this. You are to quick to annoy someone who hasnt paid the account and yet slacky on fixing ur own mistakes.