I'm upset because I gave this guy my number but he never called.
I'm sorry that you're upset. Are you interested in going out with him?
Yes, I'm interested in him and want to talk to him.
If you are interested in dating someone, it's okay to give them your contact information as long as they're receptive and also interested. Unfortunately some people may have second thoughts and don't contact you back. In that case, it's best to move on and try to find someone else to date.
But he seemed interested when I gave him my number.
He may have been interested at the time, but maybe he isn't anymore. Or he have gotten really busy. Either way, I think it's best to move on and focus on something else.