RCS

I have contacted the RCS call Centre in January to notify them that my installment due for January was going to be late as I am on maternity leave and awaiting the UIF funds to come through. I even emailed them as well as sent through a whattsapp with corresponding documents to notify them that in February I still was not paid from the UIF and that I notified them in January that interest should not be added to my bill because I am going to pay the installments as soon as the UIF funds go into my account. My accounts have always been paid. I would like to know if RCS can still add interest to my account and who is liable to pay the interest?