[Kevin]

Do deal with Sprint, tell them you want to cancel. Sound serious.

You'll be routed to the "retention" department. You then let them sweet talk you into remaining a customer so long as they give you a better plan, fix all your problems, etc. The retention folks have quite a bit more power over your plan than regular customer service folks. If you play this well, you can end up with a far better plan, more features, etc. for less money.