DEBT / LAWYERS / NO SUPPORTING DOCUMENTS

I have debt collectors and lawyers calling me weekly requesting payment but when I request paperwork to support their claims that I am overdue on an account I closed years ago they disconnect the call or just never get back to me. I cannot pay something I do not have. Is it that difficult to supply me with a copy of my signed contract with Vodacom stating when the contract started and when it ended. Please note I always take a 2 year contract but they billed me for more than that, Not only are they giving me bad credit to my name but they are not supporting their claims I owe with supporting documentation!!! Leave it to Vodacom to destroy my name for nothing!