Nokia 1208

New here, but came across this which looked great. I have a Nokia model N1208 (V5.51) and in conversations I can hear caller but they can't hear me. It's annoying but also a mystery. I haven't knowingly changed any setting — though I did drop it which may have messed things up (though it never has before!). As far as I know, it's not on 'silent' mode ... Any ideas? If so, they will be gratefully received!