it sounds like your mobile is locked to whichever network it was bought from originally you will need someone in this country to use unlock software specific for your phone...... try a market trader or an independant mobile accessory dealer who may have the software to help you last resort is sagem direct.
most common handsets from nokia,motorola,sony ericsson etc are easliy unlocked by traders also try ebay for unlockers
Barry H, September 2005