Help Can someone help?

[jewel]

Whenever someones rings me or i ring them thay cant hear me, i can hear them fine.
This only started today, my fone is not rooted or modified in any way.
I cant see anything in settings that i could try, is something staring me in the face that would sort it?

Galaxy S
UK
3 Network

TIA

 

[jewel]

Oh ffs, posted in wrong section, can a member of staff move it Galaxy S section pls