There are plenty of ways to react when you don't want to give him your number, because you're not interested or are already in a relationship. Don't be a pushover and write down your digits when you have no intention of ever texting him back once he messages you. Of course, you don't have to tell him outright that you're uninterested either. Instead, you can use one of these silly ways to react when you don't want to give him your number:
If he's a fan of Friends, he won't mind you stealing a line from Ross. When a pesky woman asks for his number, he says, "If it's meant to be, you'll guess it." This is one of the best ways to react when you don't want to give him your number, because it gets your point across, but you can still say it in a playful way so that you don't crush him.
If he hands you your phone and waits for you to type in your number, text REDCROSS to the number "90999" instead. It'll donate ten dollars to Red Cross, so he won't get a date, but he can feel great about doing a good deed--even if it is against his will.
(669) 221-6251 is a type of "feminist phone intervention." Whenever someone texts the number, a generic message will pop up. It was created in order to help out girls who are harassed by men who won't leave them alone until they have their number. You won't have to turn down the guy, because the number will do all of the dirty work for you. Check out a sample of how it works on thehairpin.com.
If you've been legally drinking, then you can get away with pretending that you don't remember your number. Even if you're clearly sober, you can risk trying this trick. I mean, your phone stores all of that information for you, so why should you know your own number?
If he gives you a slip of paper to write your number on, scribble it down as messily as you can. He'll go crazy trying to figure out what you wrote. If he likes you enough, then he'll dial every single number you could've possibly written until he finds the right one. If he does that, you just might have to give him a chance for effort--or run far, far away.
This lie will let him know you're uninterested faster than anything else will. In this day and age, everybody has a phone, so it'll be clear that you're just trying to get him away from you when you say you don't own a cell. Hey, if it works, it works.
When all else fails, you can fall back on telling him that you're already in a relationship. If that doesn't make him back off, tell him about how your boyfriend has a black belt and is always ready for a fight. It should get the guy running.
Never give out your number to someone you don't want contacting you. You're in complete control of who is allowed to talk to you and who should keep their distance. What do you do when a guy won't stop asking you for your number?