interfacing 89c51 with mobile

hi ajay,
i m making a project regarding interfacing the mobile with microcontroller to send message through the mcu 89c51. the mobile is sony ericsson t-630. i made a serial circuitary for that... and the circuitary is working fine with computer .. similarly the mobile is also working fine with computer and i send message through hyper terminal but the problem is that i m not able to get responce from mobile when i attach it to microcontroller. can any body help me in this regard

can i see the code and the circuit?
are you able to send sms via hyper term? what commands are you using?
Please once upload the code and the circuit you're using, So that i can see if there is any error in the code.