Some people report that they cannot use BBM on android smartphone while on 3G/data network connection but works when using WiFi.
The same thing also happen to me recently, while i'm on data network (3G/HSDPA) i can browse the web, use LINE, twitter, facebook, etc, but i cannot use BBM.
So here's the solution :
- go to Settings > look for Mobile networks settings (usually under Tethering & networks) > look for APN settings (Access Point Names), try using different APN
- if changing APN doesn't work, try remove proxy address from the APN
- if still not work, turn off the phone, remove the SIM card and then put back on and turn on the phone again
- trying different SIM card is also worth to try (if you have more than one SIM card and unlocked phone of course)
Use different APN settings works for me, but if none of the above solution are work for you then i suggest you should contact your network carrier (the SIM card company that you're using).
This problem is not because of the phone that you're using, it is a network setting problem so contacting your network carrier is probably the best solution, they will tell you the correct APN settings.