telling whether something will cost us if cell phone number is needed

[lsnggrp]

It always says at the very bottom in tiny print or on the terms/conditions page of the offer. Either $9.99 per month OR 99cents per message sent/received. Don't put your cell number in those quiz, ringtone, etc. offers unless you expect to pay for it.

That's very true!
Always scroll down and read the fine print, it will always say if and how much it costs.