So I changed the chrome bezel to a black bezel that I bought on eBay. I followed all the right steps and am sure I did everything perfectly.

Or I guess I didn't, since now it's pretty hard to hear my calls, even when it's at top volume. I'm sure there is nothing blocking the speaker.. It must be a hardware problem, but I don't see how it can possible be that.

Was it OEM?
Changing to aftermarket parts there is a risk in the parts not fitting, and sound quality (such as volume). You take a risk on buying them, I have a black bezel and everythings been working great, no changes to the phone at all.

Review: Black Bezel; Javelin 8900.

Everything is in there if you'd like to get a new one.
From the looks of the site they take and paint OEM. (the site I got mine off of.)

The same thing happened to me, if you look carefully the speaker area is different on the aftermarket bezel. I switched back to OEM and it solved the problem.