Microphone of my O2 xda atom purchased last year...

Question

microphone of my O2 xda atom purchased last year is not working.all other functions are fine.i can hear calling or called party but they cant hear me.phone was handled with care all the time.no fall or getting wet.need to know service centre in Mumbai.i use it for referring to different medical manuals on pda also.service provider has informed that there is no problem from their side.dr.girish gadkarimumbai 400014