Originally Posted by kirrinjones
Interesting, because I have heard the argument that just as how e-mail uses data and would not be considered roaming because its using the BlackBerry network to distribute the e-mail to your device wherever you are in the world (once your provider has a partnership), then so to the BBM uses the BlackBerry network to transmit your instant messages.
I have always been skeptical of this theory as I have never been able to test it myself, so I would just like to know from someone who has in fact traveled a lot and tried this and found the answer.
I have traveled all over the world with my BlackBerry (Canada, Mexico, Costa Rica, Qatar, Bahrain, Iraq, Afghanistan, England, Scotland, Japan, South Korea, Guam USA, Singapore, and others) and here is the definitive answer to your question:
As jsconyers mentioned, you will in fact incur roaming charges. ALL data (including BBM messages) sent and received from the BlackBerry device traverses the BlackBerry network, but it also traverses the GPRS/EDGE/UMTS network of the carrier on which you are roaming as a tunnel connection. The carrier on which you are roaming does not care about what device you are using, it just knows that you are using data and it should pass the per-kb. charges to your home carrier for billing to you. The only exceptions to this rule are the few carriers in the world that offer unlimited international BlackBerry data plans that allow a customer to use their device whilst roaming and not incur any additional costs beyond the additional MRC that they pay for that add-on.
The bottom line is that if your carrier doesn't offer an unlimited international BlackBerry data plan like some of the carriers in the US do, you will be charged per kilobyte or megabyte for ANY and ALL data that you transmit and receive in addition to the per minute and per message charges you incur for voice calls and SMS messages. It is also important to keep in mind that anytime your device is turned on, you are sending and receiving data. If you do not wish to incur the charges, you should ensure that data services are turned off from within the network options of your device BEFORE you depart your home country.
I hope this helps clear things up.