[buddhasystem]

Do I need to "unlock" my T-Mobile 8820 before I can put it a SIM card from a different carrier? Or wll it just work?

[sunkast]

That's the whole point of unlocking a device. So yes.

[Pete6]

Go to Options, Advanced Options, SIM Card. What does it say?

I can't remember the exact text when the phone is locked - sorry.

[buddhasystem]

It says:

ID: XXXXXXXXXXXX (actual number here)
Phone number: XXXXXXXXXX (actual phone number)

and that's it...

[JamesDP]

Once you reach that screen type "meppd" just like that. Nothing will pop up while you are typing to confirm what you are typing but once entered correctly you should see a screen that has a list that says "SIM, Network, Network Subset, Service Provider, Corporate." Everyone of those should read "DISABLED" except "Network" if the phone is locked. If the phone is unlocked they will all say "DISABLED."

[buddhasystem]

"meppd" had no effect