Sometimes there is an 'R' in a triangle right before the signal bars. What is it?

Posted via  Q10

Indicates that phone is in Roaming not in home zone.

Roaming

Posted using Z30 | OS 10.3.2.2339 | Radio 10.3.2.2640

Roaming.

Watch your useage when you are roaming. It usually costs a good bit more then your home service.

Posted via CB10

You can prevent getting hit with possibly substantially high roaming data charges by going to Settings>Network and Connections>Mobile Network and turning "Data services while roaming" to at least "Prompt" if not "Off."