My I-Phone speaker doesn't work when I make a call. Is something shut off?

Try any or all of the following:

1. Hit the volume Up button, the on-screen indicator will show your setting.
2. Make sure your iPhone is not connected to a Bluetooth device which you can't hear (car handsfree is a frequent trap for the unwary)
3. Test the speaker outside a call. Try playing some music, or ask Siri a question like the day or date (check Siri Speaks is On)
4. Test in a call, using speakerphone, regular phone-to-ear mode, Bluetooth if available. This will tell you if all routes are silent (probably settings) or some things work (possible hardware defect).

By this stage you should know more about the problem, and whether you can fix it yourself or you need to contact Apple Support to arrange a repair for broken hardware.