No help from RCS

I have an RCS coricraft card which fully paid up but then on 13 March I received an E mail from RCS stating that I missed a payment which I don't know of. I then contacted them via phone and they informed me that somebody did an online purchase in Durban at Game store, I stay in Limpopo and on the day of that purchase I was at work. I have never used that card online I only bought from coricraft polokwane. I was then told to Email my ID with three signatures, take photos of the card and also fill their dispute form. I Emailed and nothing happened, called again, told again to resend to another email at collections, nothing again, when you call Noone answers the landline. My credit score is now affected and today I received an Email threatening me to settle outstanding amount today account or they send my details to credit bureau. IM SO FRUSTRATED AND DONT KNOW WHAT TO DO. I CAN'T PAY FOR SOMETHING THAT I DON'T KNOW ABOUT.