I have no water coming out of my cold bathtub faucet?

I have no water coming out of my cold bathtub faucet. It has had low water pressure since my friend changed the faucet. I went to take a shower and it was barely coming out this morning. My daugter went to take a shower, and there was no cold water at all. I have a 2 faucet system with a pull on the spout for the shower. The faucets only turn a quarter turn to be fully on or off. I have no idea what brand it is.