cancellation

I insipidly responded to the Slimbetti advert as well got a call and under duress accepted the deal . thought about it then cancelled the order via email and telephone, recieved a call back attempting to dissuade me from cancellation I refused and told them I had also refused delivery and that I didn't have or want any products. Guy agreed. and said he'd call back. nothing and now I've got an sms confirming my Debit due date. I dont want to be in collections for this.