Why are there always missed calls from strangers in different places on mobile phones?

Most of these calls are from swindlers. As soon as they got through to you, they hung up and asked you to call back. Once you call back, you will be taken in by them. First, the phone bill is very high; The second is to tell you to win a prize or something and cheat you into sending money. So don't pay attention. If someone really wants to talk to you about something, they will keep calling.