contrac ended

Hi , I had an account with Vodacom at about two years ago and finished my contract with Vodacom now they are sending me a letter that says that I owe them money, I do not know how and I have settled my account in full with them I tried calling them and it is useless because at George branch at the garden rout mall, they said that there was no account listed in my name by them, and now they handed me over to the attorneys Please help