EFT Payment

I have the same situation for the 3rd time where my EFT disappears in their system. I have E-Mailed proof of my payment twice and phoned a couple of times. (I did explain that I made an error with the account number when their call centre phoned me re overdue account, but in my E-Mails I gave my name as well as ID Number.)<br> Surely this is a simple thing to trace, but every time I get told that there is a backlog on payment allocations. Does it normally take 30 days after payment to rectify payments? Surely not in any large company!