i had the same issue minus the echo once on my iphone 4. on speaker i could hear them they could not hear me. swaped out my phone went home restored from back up and they same thing happened to the new phone. so clearly my issue was software so i had to start from new phone.
i had the same issue minus the echo once on my iphone 4. on speaker i could hear them they could not hear me. swaped out my phone went home restored from back up and they same thing happened to the new phone. so clearly my issue was software so i had to start from new phone.
I'd bring it to Apple and have them check it.
If it does it every time and on every call and even after setup as new phone then it would need to be replaced.
Yup pretty much in your case it's most likely hardware. I failed to tell on my first post that although callers could not hear me through the speaker when I used voice to dial (iPhone 4 no Siri) that could pick up my voice so I knew my issue wasn't hardware
before you take it back, on the next call that u use speaker phone for on ur iPhone 5, try covering the microphone on back (between the camera and flash) and see if that helps. if it doesnt take it back and demostrate the problem to them