Call Nepal Telecom and ask them if they have a BlackBerry data plan available and to sign you up for it if they do. It will probably cost about $10 more than a regular data plan, but will give you access to push email, Internet, etc.
After this is accomplished, go to Nepal Telecom's BlackBerry page (something like
http://nepaltelecom.blackberry.com) and enter your Berry's MEID (under the battery) and PIN to register your Berry with RIM. Make certain your Berry is ON when you do this so it can receive service books.