how to use iPhone's microphone when handsfree is used?

I have an iPhone 5c (IOS 8.2.1) and use Garage-band and I want to record something on a song , but when I insert hands free , my iPhone uses the hands free's microphone to record my sound (its an earpod) . How can I disable that and use iPhone's built in microphone ? (+ I don't have a hands free without microphone) Thanks !