I signed up for a tmobile plan the other day. I talked to them online and then in a call, and asked what the taxes and surcharges would be. They said they could not tell me because it was impossible for them do so until after they generated my first bill (which coincidentally is the point at which it is too late to cancel). I did try using logic ("you already have code to calculate tax") but that obviously did not work.

Even if what you say is an issue, they can still show totals just as plane tickets do. They can say the total is $55/mo of which $13 is taxes.

I'm not sure this actually helps you, but I'm pretty sure there's a statutory Buyer's Remorse period where you can cancel within 14 days with no penalty.

I'm thinking that the first bill would probably be generated after the buyer's remorse period.

It's not -- I just signed up for a postpaid plan on T-Mobile yesterday, and the receipts included the first and second months' bills (for service and taxes).

If you do it on the web they make it very plain that $0 is due now. They do say the plan will be $45/month but there is absolutely no indication what their additional fees will be nor what the taxes will.

I'm in California. Maybe you are in a state where they actually have to provide this information?

I'm in Oklahoma, which traditionally doesn't have much in the way of consumer protection or information laws. It's possible, though I think it's probably because I bought it in a physical store.