*********** DEPARTMART! - Letter of demand

As Background, I was part of Nashua mobile and since 2009, I have NEVER had billing issues. Around Oct 2014 Altech took over and the ******* started! I had taken a second contract for my wife June 2014, no account issues, When altech took over, they decided to debit a company I left in 2010 for MY Second contract. After getting this resolved and ensuring that they have the debit details corrected, they debit me correct the next month. The following month, the miss the debit. I called in and was told there is a credit so no debit necessary,As I have no faith in Altech, I called in again few days later and was told, I am in arrears.So I asked them to debit my account same day. Next month debit was fine.Last week I find out my wife's cell is hard locked by credit as I am 90 days in arrears(statements reflect up to date) and I now get a letter of demand. How ALTECH is this possible, when YOU CONTROL THE DEBIT, HOW CAN THE STATEMENT YOU SEND ME BE UP-TO DATE BUT I BE IN ARREARS, I have called, shouted and nothing. Your word is nothing, I want PROOF of this being RESOLVED ONCE AND FOR ALL AND CONFIRMATION THERE IS NO IMPACT ON MY CREDIT PROFILE due to YOUR INCOMPETENCE!!!