Cobros

Hello everyone, 

I have a debt in collections with T-Mobile since I started flight school. I called T-Mobile, and they gave me the first agency that had the debt. The original company sent it off to a third party, and I'm honestly having difficulty finding this "second company" to settle it. I called T-Mobile to see if I could settle the debt directly with them, but I don't remember the pin to my account. I do however remember my old number and the security questions to my account. If anyone has any advice or suggestions please let me know. I truly need to get this matter handled.