UNISA doesn't answer their PHONES

been receiving sms's for a while now saying I have an over-due account from 2014. I have absolutely no information whatsoever. Trying to call UNISA as well as email and all i get is voicemail and no response. Managed to find my student number, however I can't remember the password. Still no way of getting my password or any help!!! Totally frustrated as I have now received an sms saying my account will be handed to a debt collector?? If I could get some help to **** see the amount and how to even pay I would!!! Really pathetic from UNISA's side.