Front Microphone Not Working on iPhone 4s?

Whenever I receive a phone call, the person on the other end cannot hear me unless I turn the speakerphone on. As you can imagine, this is really annoying! When an app such as Snapchat takes a video, there is also nothing but noise, but videos taken in the official app are fine. I believe the front-facing mic, wherever it is, might be broken. I know the other mic must be okay. Are there any solutions?

Thanks

Noah