It can be difficult to judge someone's personality based on one phone call, and doing so might not be really fair. Think about what made you ask this guy to be your date. The better you know him, the better you can figure out what he'd be like at the actual dance. If you have been attracted to his looks or manner without knowing what his personality is like, then maybe his immaturity is a sign of how he might be at a dance. Or he might be nervous about going to a dance with you, and his immaturity is just his way of showing it.

You could cancel with the immature guy, or you could go to the dance and see what happens. If you cancel you'd have to explain why, and while it may be tough, an honest approach is really the way to go about it. You could try talking to him and bring up that you wonder if you and he are compatible enough to enjoy going to the dance together. However, consider how you would feel if someone said this to you. You might be relieved, or you might be really upset or insulted if you had been looking forward to going together.

You could decide to stick to your original plan and go to the dance with the immature guy. He might turn out to be a great date once it's just the two of you, or he could turn out to be a friend. Or he could turn out to be as immature as you think and maybe the dance won't be as memorable as you would like. However, going with this guy would be following through with your original plan.

Whatever you decide, keep in mind that this dance is just one of many you will go to, and if it doesn't turn out to be the greatest night, that's OK. You can still enjoy yourself at a dance with your other friends, even if you and your date aren't having the best time together. It might work out that another guy you like doesn't get along so well with his date, and you may end up dancing with the one you like after all.