Complaint

I have been with vox telecom the past few years, it happened that i lost my sim card, i called them and sent emails informing them of the matter, months later they sent me a statement with the balance, i settled the amount of R600 which i still have the proof. Ever since than i never utellised the sim card as i was waiting for new sim...last year in Feb they swnt me an email stating that i owe them R900, i made several dollow ups with calls and emails as to were disd that balance come from, i have proof of my payments, i even have proof of closure letter that was sent to me . today i recieved an email stating that they will hand my acc over to the attorney's.... I have all the proofs I have been making follow ups since last year they never got bavk to me with explaination..