Naughty or Nice?

Today is the first day of Christmas break and Kaleb & Noe are already tormenting each other, and we're just having breakfast now- ugh! I'll get them working on an art project as soon as they're done eating. Anyway, I was thinking how nice it is that they believe in Santa. It's great that I can remind them that "if you're naughty Santa will bring you a lump of coal instead of a toy." Here is a little conversation we had:
Kaleb: "Mommy, Noe did blah, blah, blah, blah, blah."
Noe: "Mommy, Kaleb did blah, blah, blah, blah, blah."
Mommy: "You two better be kind to each other or I'll have to call Santa."
Kaleb: "What is his number?"
Mommy: "It's just for parents to know. If kids know they can't get gifts from him."
Kaleb: "Will you give me the number when I'm a daddy?"
Noe: "No Kaleb, Santa will give it to you when you're a daddy."
What will I use when they can't hear the bell jingle anymore?