Can't hear the other person

Your mobile earphone is damaged. Replace it at your nearest sony ericsson service center.

I have a guide for it on my site. It is pretty easy to take apart the W810i.

How to Open Sony W810i

To upgrade the software of your Sony w810i cell phone, you can download the upgrading software from Sony's website here:

http://www.sonyericsson.com/cws/support/softwaredownloads/detailed/updateservice/w810i?lc=en&cc=us

adjust volume during aa call with the volume key up

Well, try to record something onto your mobile and check if the recorded track echos at different instances...If yes, have your mobile speaker checked withthe vendor.. If not, clean up the vicinity of the speaker... 

Yeah well better take your mobile for service to a Sony Ericsson showroom..Even i had a same problem in sony w810i which got fixed after a service..Thank you!!...

just connect your phone to pc through data cable and go to sony ericsson site and update your firmware........
but take care while updating ......

I had the same problem with that phone... while manipulating the mobile part (cover) you can slightly improve the volume.
Another point to check is the button on the side of the phone which allows to increase or lower the volume: it could happen that you turn the volume low without noticing it...
My solution was to replace the phone.

just check the volume up and down conector i think there is a shorting in that

i had a similiar person who came to me with the same speaker problem try takin ur case of and where ur speaker is that u put up to ur ear clean it out with a soft cotton bud slightly damp otherwise go to ur nereast mprc ( mobile phone repeair company) they r very competitave it cost the person 25 pound and they did it while he waited if u want the numbers let us know