So at some point you sent in a Samsung Galaxy Note5 for replacement. T-Mobile claimed they didn't get it, then said they found it, then said they didn't get it again, but ultimately got it. You've filed a theft report and contacted your state's attorney general since the company is tacking on late fees.
Is this the gist of it?
My suggestion to you is to get off the phone and write a short, polite email to t-mobile customer service explaining the situation and asking all late fees and penalties be removed from your account. Its important that you email be clear and include relevant information.
Dear Sir or Madam,
My name is Xxx and my account number is ####. I returned my Samsung Galaxy Note5 on (date) for (reason) via (method) per (whatever instructions you got). For 6 months t-mobile claimed the phone wasn't received, despite numerous calls trying to resolve the issue. In (month) I received word the phone was found, then again was told it was lost. In September I was told it was once again found, however, my account now has a substantial amount of late fees and penalties because of this.
I returned the phone on (date) per the instructions given to me by (name or agency). I don't know what happened internally at t mobile that caused the phone to go missing, but I upheld my end of the contract. I request all late fees and penalties be immediately removed from my account.
If you shipped the phone via a method that included tracking, then definitely include that and show the phone as received. There is no need and it won't help to mention your health issues or accuse them of ruining your health. This is a business issue, treat it as such, although you can ask for a month or two of credit due to the inordinate amount of time you've spent trying to resolve this.
Give customer service a week to respond. If not, or they don't respond favorably escalate via the first company contact we have, located at the top of the page in the black bar. Do not email all the executives at once and do not start with the CEO. Either will decrease your chances of a successful resolution.
Best of luck, and let us know of any questions or updates.