AT&T put a derogatory mark on my credit because of a modem that wasnt returned.. is this disputable?

If you did not rtn it, yes. But you can still dispute it

Yes, but it didn't return it then it will go back on unless you return it or pay for it.

Did you return the modem? Did you get a receipt when you turned it in? That's your proof when you dispute this. If you never returned it or don't have proof that you did, there's nothing to dispute it with.

Everything is. But without some proof, it will go back on your report.

Define derogatory. If they said you failed to return equipment because you failed to return it then it is the truth. How are you going to dispute the truth?

Each time you dispute it lowers your credit rating another 25 points. It's unfair but that's what they do.

No. What's to dispute you didn't return it ?

Do you have your receipt from when you returned it?