Recently I was on a trip with my family down to Florida, and on the way, my phone told me that I was "roaming". Or, I suppose, using the Extended Network. On my phone, I have data roaming unchecked. Although my phone shows the symbol of roaming I was in the USA, so technically it shouldn't be "roaming", just using the extended network... I heard if you go outside USA, even if you have the unlimited data plan, you get charged for data use.
My questions is: Do you get charged for data use when you use the extended network in the USA? Should I check data roaming if I know I will never go outside America?