Never do business with Phone choice

Since last week phone choice kept on phoneing me and telling me i owe them money. After numerous emails and calls they acknowledge that I paid every month and that they have received my December payment. I got I phone call now from debt collector's telling me I must pay. So how far is this company willing to go with this. I really want to sue this company now. I also record our conversations. I have all the emails were they confirmed payments received . So who exactly is going to pay those debt collector for this nonsense now.