I need to put my speaker on when calling

Hi,

First use a strong light and a magnifying glass and check if you can see if the voice inlet hole on the bottom edge of the phone appears to be blocked at all. If it is or if you’re not quite sure, do not use a pin or probe to try and clear it as you may damage components in the phone. Try using a vacuum cleaner to suck out any obstruction.

If you still cannot be heard on a call, most probably there is a problem with the primary microphone

Here is a link to the ifixit Fairphone 2 Microphone Module Replacement guide that will help.

There is also an app available on the phone that allows you to test the primary microphone as well as a lot of the other hardware in the phone which may also help.