What does it mean when you dream of someone then they call you?

That will depend on who you dreamed of and how long afterwards they called you.

If it was a dream of your best friend and you call one another every day, then most likely it has little or no meaning.

If the dream was about your grandmother and you only talk to her once a month, then it could be your mind telling you that it is getting close to time to speak to Grandma.

However if you dream of a call from someone you don't often hear from or do not know and they call the next day, you may have experienced a minor precognitive dream. If you remember the conversation, and it is the same, then you may have experienced a major precognitive dream and might want to start a dream journal, just to see if it happens again.