I m not able to hear any calls in it what to do

I would recommend,

1) take your battery out and place it back in to do a full reboot and see if that help.

2) try a headset to make sure its not the actual sound card that wen dead.

3) do an update via http://us.blackberry.com/update/

4) at your own risk you may want to open the phone to make sure the speaker did not move away fro the contact and if id did re-seat it - you may also want to clean the contacts with alcohol.

Are you able to hear calls if you put the phone on speaker?
You can try turning off your phone, taking out the battery, putting it back in and then powering on again.
You should also try contacting your carrier- this could be an issue with their service, not your phone.