Product: Debt collection

I am disputing a {$580.00} charge from XXXX who have been sending me a bill for a XXXX account I NEVER activated. I received a bill from the company every month for three months until it was sent to debt collections. Every month I received the bill I would call XXXX, the technician would confirm that I never activated the lines and that they would take care of closing the account and that no money was owed, only to receive another bill with a late charge the following month. Here is the complete story : I was interested in switching phone companies back in XXXX from XXXX to XXXX. I received " cards/chips '' from XXXX that were to be put into our cell phones when we were ready to activate then, I was clearly instructed not to cancel my current XXXX account until we activated the " cards/chips '' into the phones, but they did not send all the cards for the XXXX lines and when they told us to go to a XXXX store I said that wouldn't work because my elderly parents were out of state and I wouldn't be able to get them to a store, so I said forget it, I don't want to switch to XXXX, in which they said XXXX okay, we will keep this account open just in case you change your mind but you won't be charged anything ''. 
Sure enough, I received a bill the following month for {$300.00} for all the lines. When I called XXXX, they said " hmm, that's strange because we usually cancel with the other phone providers when you switch to us but since we can confirm you never activated these lines we will take care of this charge and close this balance ''. One month later, another bill with a late charge. I call again to both request to close whatever account is open and causing this problem and to see why the balance was not settled. Their response " hmm, let me put you on hold '' I wait on hold, the technician then says " yes I confirmed with our staff you did not activate these lines and I see notes here that there was an issue we were supposed to reach out to you but the technician didn't but I will take care of this and you will see a credit for {$250.00} because that's the max I can credit a month but don't worry the following month the rest of the balance will be paid I assure you ''. By XXXX, I get XXXX ( military ) only to come back a month later to a letter from a debt collector and XXXX will no longer take my calls. The debt collectors are now just essentially demanding {$580.00}. I called the debt collectors initially, they said they will only take a statement in the mail disputing the charge because I am from the state of XXXX, then they will reach out to XXXX and we should hear back within XXXX days. So I sent them a statement last week and called them today to confirm if they received my letter in the mail. The debt collectors responded with " yes and XXXX proved you owe the charge so how would you like to pay today? ". I challenged this, I said you told me last week it would take XXXX days how have they already received my letter in the mail from last week and responded? '' She then said " Oh you sent the letter last week? In that case we haven't received your letter yet but I am confused because XXXX already proved you owe the amount '' I then said " Is it just a bill? '' She said " Yes '' and I said " how does that prove anything they send me that bill every month? ". She told me to just wait and call back next week and she would speak to the XXXX. 
At this point I was now not trusting the debt collectors, and saw on the letter from the debt collectors that I could review the statement on their website. When I went to the website It would not let me view anything and said that they received my dispute, verified the charge and have sent it to the XXXX credit bureau. I was beyond furious obviously. I called the debt collectors back, spoke to someone else, who claimed there was a double dispute on the file and to call back next week. I am literally praying that all the phone recordings from XXXX and the debt collectors are available somehow. I don't understand how I owe XXXX money for an account they repeatedly verified every month that I called them that I did not owe. Thank you in advance for your time and support.