WRONGLY BLACKLISTED

I have never taken any cellphone contract with Nashua, to my surprise i am receiving numerous calls that i owe Nashua mobile cash, when i told the agents, can this matter be investigated and i want feedback - Noone bothers to send me the info. Again Kwazi called now, SAYING I AM BLACKLISTED- for something i dont know about. DETAILS: Miss NA KUBHEKA - *** I DONT HAVE CONTRACTS WITH NASHA - I BUY MY PHONES CASH.