Cellc amd SSDA attorneys

I had a contract will cellc for two years and when the contracted ended i wanted to cancel so i foned cellc to cancel and the agent told me i must pay the last month and a cencelation fee witch i did and now all of a sudden 4 months later im getting calls from SSDA attorneys saying i owe an ammount but when i call cellc they cant help me becouse my account has been handed over and SSDA attorneys also cant tell me why i owe cellc and besided cellc is in breach of the poppi act for sharing my information to a third party without my concent. I havr never recieved any fone calls from cellc to say that i owe any ammount