sim cards

Hello

I am new to PDA's and would like to check if anyone is usuing international sim cards with the ring back facility to obtain cheap rate calls. These cards work fine on my mobile but would like to know if anybody is usuing one with a PDA.
You probably already know the details but you purchase the card, top up with the money, dial the 00 type international number, the line goes dead for a few moments and then the phone rings back and you answer in the usual way and hear the ringing tone waiting to be connected.

Thank very much