If you wanna use your sim for your data connection. Try telenor and Zong depending on the city you live in.
Our telecom services dont have 3g Spectrum yet. And its only Edge/GPRS but EDGE services here are really fast as compared to EDGE networks in other countries.
If u have tmobile connection/phone, u need to call tmobile customer service and provide iemi number of your phone. They will send u unlock code free of cost. I recently unlocked my android phone.