Q: my phone will not make calls unless it is on speaker. how can i fix it??

Try This...

Close All Open Apps...  Perform a Reset... Try again...

Reset  ( No Data will be Lost )

Press and hold the Sleep/Wake button and the Home button at the same time for at least ten seconds, until the Apple logo appears. Release the Buttons.

http://support.apple.com/kb/ht1430

More Info Here  >  http://support.apple.com/kb/TS1630