Why won't my iPhone 5S let me hear calls and mute my microphone?

When I call, they can't hear me and I can't hear them. My microphone won't work with Siri either. Help!

Added (1). And could RadioShack repair it?

Go to the Apple Store, they'll deal with it for free.

It sounds like you have a defective phone. One more thing you can try is the Voice Memos app. If that doesn't work (it probably won't) and if the phone is new, you should return it to wherever you got it from for an exchange.

RadioShack will charge you for a repair unless you bought the phone from them. An Apple Store will indeed repair it for free if it's still under warranty, but if the phone is new, an exchange is faster and easier.