Sunita Ji, You can definitely use your tri-band GSM phone in Nepal. If you bought this phone through t-mobile, cingular, att wireless. verizon or other provider your phone is locked with their codes. You can take your phone to this cell phone place in New Road...near pipal ko bot...in front of a photo shop....go up the stairs and they wl unlock any phone in the world...they will charge 1500 - 2000 rupees. Also if you want to be a brave soul and do things yourself...you need to buy a dongle...or cable to connect your cell phone to a computer port and then flash the cell phone memory using software like "Prodigy" ... hacked versions if you can find out there in the Internet. Have fun.