Wireless International web access

Does anyone know if it’s possible to use 2 different wireless servers on one cell phone?
My boss has a Blackberry and when traveling to Mexico discovered that Sprint had mislead us as to the coverage for internet useage.
We don’t really want to have to change wireless servers, but we need international service. AT&T has great international coverage. Help please, boss is ready to throw the Blackberry out into Las Vegas traffic.