Account paid in full & all of a sudden I am owing?

I have an account with Edgars which I paid in full in August and now I a getting endless statements and payment reminders of a R173 that I a now owing Edgars. How can that be? How can 00 Zero Zeri bare interest? My interest is on What? They tick boxes for useless magazines and insurance which people did not chose. I surely did not join anything and as for insurance, since I nothing