I got a call from this number about a payday loan. She said they are charging me with fraud. And asked if I want to settle out of court. I told her I don't know what she's talking about and I would have my attorney call her. I asked for her name phone and address and she said that's okay a summons will be served to you. And she hung up. Who is this? Do they warn you before you are served?

No, when you are served, the process server will just come to your residence or whatever address they officially have and you will be served then. They do not warn you.

If she is hanging up without revealing any specific information, it is a scam. They attempt to scare people into paying monies that are not owed. Do not answer again, ignore the calls, call your attorney with any questions if you are concerned.

Do not settle out of court, there is no true court case.

Fraud is a criminal offense.  No one calls you to warn you that you are going to be charged criminally, the police simply come and pick you up.  This is an extortion scam by criminals trying to scare you into paying.
Also, it is illegal to pay money to have criminal charges go away, which is what they are trying to get you to do.  That is called a bribe and is illegal.
To learn more go here:
Read up on your rights here, get template letters to send and also make a complaint at this government site:  http://www.consumerfinance.gov/
Also file a complaint with your State Attorney General's office.
List of State AG’s offices:  http://consumerfraudreporting.org/stateattorneygenerallist.php

Thank you both sooo much!! I have been stressing about this all day.

No problem, glad to help.