iPhone 4s - random numbers not hearing me

[Anonymous]

During the last few days around half of the people I've called on my iPhone 4s haven't been able to hear me (they get silence) though I can hear them.  I live and work in London UK.  Any ideas?

Thanks

Andy

[Anonymous]

I have to ask has the phone been dropped recently as there was a few incidents where the IC (chip) had weak solders points?

Sorry to ask but best to eliminate that first.