Several different issues:1) You can't be made responsible for a bill by someone else putting your name on the bill--unless you had agreed elsewhere (e.g. in the lease) that they could do this. You may not be liable for anything if you can prove that you never authorized this, though at this point (post judgement) it may be very difficult to prevail on this argument.2) If you are one of several names on an account or bill, you each are theoretically liable for the whole amount (though if you end up paying more than your proportionate share, you may be able to sue the other people on the account for their contributions). You could possibly settle your "half" of the bill with the utility (or whomever is suing you), though a settlement is voluntary--the other party would need to agree, and you'd need to make sure that you get a release that clearly lets you off the hook for the rest.A lawyer can help you with both 1) and 2) above. Good luck.