I shouldn't have said it won't cost you son anything to call you in my earlier post (I was thinking it would be a local call but now that I reread your post...). It will cost him whatever it normally costs him to call your cell number, it just won't be an international call.

"Locked" cellphone means it will not make/receiver calls with a SIM card from a different cellular carrier. In your case, the phone cannot make/receive calls with anything other than T-Mobile USA. That's what it means to be "locked".

You really can't tell if your phone is locked or not with a brand new Italian SIM card, as that card isn't yet activated. [And I don't know if it's possible to activate an Italian card in the US.] The best way is to find someone with Cingular or AT&T's GSM service, and try their SIM card with your phone. If you can make/receiver calls with a Cingular/AT&T SIM card, you have an "unlocked" phone.

Again, the "lock" we keep talking about isn't about the SIM being physically locked to the phone. The "lock" means the phone cannot be used with other SIM cards that's not your original carrier, i.e. T-Mobile USA.

BTW, you said you receive the phone and the SIM card today. Do you mean your T-Mobile SIM? Or are you talking about the Italian one?

Who did you order the phone from? What plan are you getting?

Finally, you don't need to do anything to switch frequency. A tri-band phone will look for all frequencies by itself.

If the son is using a T-Mobile cell with a US sim card, the call to Mom will cost $0.99/minute.

If you leave your normal-use sim in your T-Mobile phone, ALL calls received/sent with your phone cost $0.99/minute while you are overseas. When you return to US, your calls return to the service plan that you bought.

If you get your T-Mobile phone unlocked, and replace the US sim with an Italian sim, then the rates are based on the Italian sim / cell system; also, the phone number will now be different.