How to send a circle of friends gracefully, saying that children can't talk on the phone for the time being.

Take a photo of the children attending the online course and match it with the relevant copy:

You are looking for my friend, because my child is having a class online on my mobile phone, and I can't answer the phone. You can leave a message if you have something. I'm sorry if you saw it.

Other elegant ways to make friends:

Share life feelings; Self-portrait photos should be available, but not too many. Taking selfies every day will only make you look narcissistic. After all, a person's connotation is the lasting charm. Usually you can write a little about your feelings about life and share your views.