Q: how do i change the phone speaker volume?

while you have something playing... ie songs from your music collection, you should be able to tap the screen and move the slider, or use the volume button on the side of your handset.

If its not working after doing either of these, you have problems.

if your talking about while your in a phone call, you just use the buttons on the side of the handset.

Have you removed the plastic shipping film from the front of the phone?

Then you probably have a hardware failure.