Sick and Tired to try and solve the problem

During May 2018 I received a call from Edgars Stores stating that my account is in arrears I have not used my account since 2015 after numerous enquiries made by me I was told that air time was bought on my account I have not purchased any air time as I have a cell phone contract and as I am a pensioner I do not require additional air time I have been up and down to Edgars Stores to try and solve this problem but also receiving call from a debt collectors company threatening to have me blacklisted but when speaking to the people on the phone they said that they can see I have lodged a complane and it will be reversed which was not done I have filled in a dispute form and a affidavid handed it in at Edgars but still receive calls from the debt collectors. During one of my visits it was told that the cell phone used to buy air time's number is the same as mine except for the last number that differed I hope that this matter can be solved once and for all I have never before had any bad records