I just got this call on my cell.  Now worried that it might be someone who is using my number

I received a call from this number and they didn't leave a message. When I called back, there wasn't any answer.

I just received a call from this number and she said she was from Southern California Edison.

I received a call from this number. When I answer the line. I don't receive a responce & when I call the numer back.. there is no answer.