Changing SIM's

[BigBit]

I have a T-Mobile MDA (US) upgraded to v2.26 ROM. At this point the only SIM card I have installed in the phone is my standard T-Mobile SIM card.

In about two weeks I am headed to China, and I would like to buy a local China Mobile SIM card (pay as you go type) and install it in my phone, as the per-minute rates are only $1 versus $3 for T-Mobile.

Am I going to have to unlock my phone in order to use this second SIM card? If so, what is the correct procedure to do so?

Thanks to all in advance for your help.

[ADIP]

connect the phone to the pc
run the program on the pc
it will give you the unlocking code
you will need to enter this code when you use the new sim

good luck