Burning a hole in your pocket- redefined

The summer break is fast approaching, so I taught the song Summer Holiday to my class and they loved it.  

RN: Ma’am, we will miss you in the summer holidays.

Me: I’ll miss you all too.

AJ: Do one thing. Take our phone numbers, and call us when you miss us.

Me: That will burn a hole in my pocket.

AJ: Ehh..? Burn a hole in your pocket? What does that mean?

Me: Uhmm..I’ll give you a clue. What do you keep in your pockets?

FM: Purse?

SS: Mobile phone?

RN: Aaaaaaah! I know I know!!

Me: Ok...tell me.

RN: If you call up all of us (28), then your mobile handset will become hot. When you keep it in your pocket, it will burn a hole in your pocket..

Me: ....................