Originally Posted by DancingFool
If you were living together, then he is fully responsible for half the bills. It's not any different than if he was renting an apartment and got sent away for work. He'd still be liable for the rent, utilities, etc. Him being out of town is not an excuse for not meeting his obligations.
That said, it seems like he is doing a super slow fade out of this relationship. Moved out, not paying his share of the bills, etc, etc, etc. He is checked out and I dare say he is one of those extreme cowards who can't simply end a relationship like a decent human being. He'd rather make it so painful for you, that you finally do it for him. Go ahead and oblige him and spare yourself any more grief and frustration with this.
At this point you are, for all means and purposes, single and living as such. You do not need to be paying for his phone on your plan. Cancel him out. If he wants to go get a prepaid phone, that's his problem. You need to take care of you and do whatever you need to do to pay your bills. Cut off the dead weight, aka fiance, and move on and do what you need to do to get back on your feet. Ultimately, it will be better and easier for you that way.