I used to have T-mobile several years ago. Shortly after I cancelled my account it went to a collections agency, I C Systems Inc. I paid them a few years back but don’t have any of the documentation and need to prove it was paid for employment reasons. I have called and they have zero record of my bill, paid or otherwise. I have an acct# from I C Systems Inc but they can’t find me in their databases at all, even using my SSN and birthdate. What can I do?