Blackberry Messenger
 

Blackberry touts this service as FREE to and from anywhere in the world.

However, TMobile USA Cust Care says that if used while roaming, there will be roaming data charges, which can add up pretty quickly. Anyone have personal experience with this for the facts? I think that possibly the TMO rep was guessing.

Similar situation with the BB/Wifi calling feature. Not clear that if the phone is WIFI connected to a Hotspot while roaming, if calls made back to the USA will be billed as if originated in the USA... Again, the Rep might have just been winging it, or trying to discourage use of the UMA feature this way!

It is possible that BBM use will be covered under T-Mobile's Unlimited International E-mail plan that's 19.99/month (prorated). Perhaps you could change your APN to blackberry.net & see if that can lower the bill more after having the option on (this ought to make all traffic go through RIM's servers).

When using UMA, your phone (and bill) should behave as if you were in the US, so any minutes & texts you use would come out of your bucket and if you have unlimited night/weekends, remember the time zone is likely your home time & not where you are.