Sportscene **** service

I went to pay sportscene like i always do and my instalment was 495.i went instore told the lady i want to pay instalment and she said she cant see amount system is offline .so i said its 495 she took payment gave me receipt and we left i never checked .few weeks later my hubby gets q call its his account and many more calls saying we didn't pay .when i called the call center they advised me that because system was offline she most likely just took what was the min amount . I DONT UNDERSTAND WHY THE 250 WAS TAKEN ????? ITS CAUSED SO MUCH STRESS AND ANXIETY .we pay every mth and then they make a mistake and we penalised????