You have choices, the 1st would be to pay the ETF's, which is not feasable for you at this time. The other option would be trying to sell your plan to someone. You can do so, and throw in the phone's you don't need as a gimme. The problem is you have to find someone that will be able to be approved by AT&T or pay the Deposit, if they are required to have one. You can google Plan Sales or something similar and find a site that does it, or you can try posting it in the For sale forum here.
Good luck to you with that, hope you can find someone who needs the plans.