pick and pay store account

i have a store account at pick and pay... this month i was slightly late with my payment(R275) on my statement) and paid R280 on 11. (Monday).11. since i was away and had no access to any banking. today(2 days after payment) i get mail that i have to pay extra 75 rand if i still have to pay;... but...it also stated, "if you paid already please ignore this email" so, i actually was supposed to ignore... but i wrote anyway just to tell them i paid... now i get a reply that i still have to pay this 75 rand extra .. can't be right, it is in disagreement with the email that stated that i have to ignore mail if already paid... so... what now... also i had cases when i was turned away at pick and pay tills because nobody was on duty who knew how to deal with my monthly payment. i spoke to manager... asking why nobody knows how to handle store acc. payments; yet, it is a service offered...