Unfortunately I cannot call *611 from Mexico, I get an automated message in Spanish that I do not understand, and it ends the call with a message window that says: "You cannot make outgoing calls while call barring is on". I cannot make any outgoing calls to friends or family either, regardless of adding 0 or 00 before the 1 or +1.
I'm a little annoyed at this! I could have paid much less money for texting only if that is all I am allowed to do!
If you added a Roaming Add-on, you should have automatic access to the network in Mexico.
I suggest that you turn your phone off, remove the sim (if possible) and then turn the device back on. It should search for the closest carrier. If that doesn't work, please go to your Settings and do a Manual Network Search.
Once you have a signal, *611 should be accessible.