Question for people employed by Tmobile or have been in this situation only please?

[CaliforniaMommy]

If I decide to start a line of service with Tmobile online-will they charge my credit card, and then let me know if I need a deposit? If in fact a deposit is needed how does that work if they already charged my credit card? Lastly-if I decide to keep my current phone carrier and do not want to pay the deposit how do I get the money they already charged to my card back? Any help would be wonderful thanks!