Has anyone come across this before? Nobody can hear me when I'm in a call but its no problem when on speaker phone or using the voice recorder app.

iPhone is out of warranty so my choices are £120 apple repair or £100 excess on my insurance....

The microphone can't be broken if it works fine while on speaker and I've done a total restore of the phone and a 'DFU restore and its made no difference.

Any ideas?

When holding the phone, could you possibly have any part of your hand covering the mic?
Ive done this a few times myself.

Does your phone think headphones are plugged in?

Press the up and down volume button and see if it says headphones.

I have had this before and compressed air fixed it.

Would that replicate the symptoms? The volume buttons work as normal so I don't think it's that. I did try n clean the headphone socket earlier today though as I'm selling it on eBay at the moment

Sometimes it's caused by the phone thinking that headphones are plugged in so it won't use the microphone even though it's working fine.

Even though it's out of warranty it might be worth popping into your local apple store.

Yeah I've been to apple and they cleaned the microphone and did the DFU reset bit couldn't suggest anything else except the £120 exchange/repair thing

Okay I've plugged some headphones in and took them out and now apparently on a call I sound like I'm across the room even when shouting into the phone.

A small step forward...

Just to finish off the thread, its working completly as normal now

has it become damp (after rain, or in a sweaty pocket) and is that effecting the mic?