Have you ever messaged your number neighbour?

I was talking to a friend today and they mentioned their "number neighbour".

Being completely oblivious to what she was talking about I said no.

Apparently people message their phone number either 1 digit up or down and say hello.

I told her I wasn't sure that's entirely a sensible thing to do.

Has anyone else done this?

Edit: I'm glad I'm not the only one who thinks this is weird.