I can’t hear people on my phone unless it’s on speaker.

Can you hear at all? If you can hear but at a very low volume, your ear speaker grill is probably covered with dirt and grime. You can gently wipe it with an alcohol pad, then brush the debris off with a hard bristle toothbrush — don’t use the air spray because that would just push the dirt inside, clogging it even more. The proper way to clear out the blockage is to open the phone up then take a part the ear speaker and the flex, and blow away the dirt from the grill (you can use the air spray from outside in or inside out .) Be sure to hold the screen up at the light to check that the grill is clear.

If you cannot hear at all, it is most likely that your front ear speaker/camera flex is bad. You can order a new one and replace it.