Charging me exorbitant monthly fees, because THEY owe ME money?!

A few months ago I returned an item bought on my store account. I then immediately requested the balance of my account and settled the amount outstanding. The next month I received a statement from Woolworths, showing this return value as a credit. This was fine, obviously the return did not immediately update my balance due. However, I was SHOCKED to see that the montly account fee of R52 was deducted from my account! This for having a CREDIT balance?! Woolworths owes ME money? I sent two emails about this over the last few months, but NO-ONE has responded. I am going to close my account due to the blatent theft and their poor customer service. I can't even do this online on their website, as their "financial services" has been "under construction" forever now. Ridiculous.