Dear abhi I think I know what u r missing now try doin it as I say
First put your phone in diag mode , than connect it to qpst and see which com port it is connecting to. Close qpst and start cdma workshop now first connect the phone to cdma and select the com port than by clicking the connect tab connect the phone than click on read tab you will see all your phone details appearing on the left which now proves that u r connected, go to security tab and put your spc and click on send , u wil get a message saying phone is unloced now do the nv write process, u will get the message to send spc but ignore it and click on ok. You will get a message in the bottom saying 36 items written successfully, now shut down cdma , it will ask to rest phone press ok and your phone will reboot. U r done. Same way u can write the prl.