[tsac]

Ok so if none of the carriers in the country your in have a blackberry plan or restrict the amount of data then you cannot do what your trying. When traveling in other country's or areas where you need to go off your normal carrier and "roam" to another carrier your under their rules for use. Generally the phone will work for calls but in some cases that's all.
If you can find out what carrier your using locally it may help to research or give them a call and see if they allow data use while roaming from other company's customers.

the other thing you can do is use their service, if they support blackberry