if you pay you account on time they bill you a fee

i usually have good service at woolworths but the standard of service has dropped. i have never received a monthly account bill except for their interest. i started paying my account earlier avoiding the interest that was when they started to bill me a monthly account fee and called to query it. i called their call center as was advised that they would get back to me. i never received a call since i decided to wait for my statement and found out that it was billed. i went into the store explained my story to the lady at the store who didn't even seem to care she just took me to the phone and said i should speak to someone in the call center, yet again over the phone she could not explain why they never called me back and did not even apologize for that. i walked into a different store pretending to open a new account and asked them about a monthly fee they explain they don't charge monthly fees just their standard interest. i cant believe woolworths and their pathetic service