Sony Ericsson W580 / S500

Ive had my 580 for a few weeks now and i've been having alot of signal issues, and by alot i mean dropping calls anywhere from 3 to 10 times a day. a co worker has a cheap pay as you go phone with her att sim card in it and she gets better signal than i do. is there anything that can be done to boost the signal? im pretty sure there isnt but i figured it doesnt hurt to ask. thanks