I received a short message, but I don't know who sent it.

If you are a serious person, you can call 1 14 to ask the other party what number it is!

Maybe it's an old friend of yours, but I don't contact much now. You can check with and find out where the number is. Then contact your old friend and see if it's his number.

Now many of them are spam messages, so it's better not to reply.

Some time ago, I received several strange calls from Beijing in the middle of the night. I didn't answer them. When I asked my classmates, there were many advertisers. When you call, it will be bad.