RCS say I owe them but I have a paid up letter

I'm posting this because I want people to be aware of the sloppy service from RCS. I paid my account up to date in November and had to nag them for a settlement letter and was fortunately enough to finally receive it. Although I settled my account they say I owe them even more money @ the amount does not correspond with the threatening SMS' they have been sending me even although I have a paid up letter. I have not received a single call from them how unprofessional for a corporation.

SAVE YOURSELF TIME, ENERGY & FROM DISASTER - DO NOT USE THIS SERVICE