EFT

I'm struggling to understand why a big company like this can have an EFT facility but yet fail to update the accounts. I made an EFT for my account using the reference number which I got from ackermans customer care and emailed the proof of payment. To my surprise I keep receiving calls stating that I owe Ackermans whereas I paid the full amount due>Why don't they jus tell us that they do not accept EFT and we should just pay in store. Why don't they just reverse the amount paid because it cant take two full weeks to clear the account