Employee alleged theft

I have an urgent question to ask. I was recently fired for alleged theft. employer claimed that I was making fraudulent refunds and also accused me of taking money from their till. The only thing that I can remember is that I made couple of changes like breaking down bigger bills (my own money) into smaller ones from the register as my kids' schools do not take card payments and I am think that maybe their camera caught it and so they accused me of theft/shoplifting and fired me. This was last month. I just received a call from a law firm indicating that they are representing my employer and that they have filed a civil law suit for shoplifting with them (the law firm) for me to settle with $800.00. Here is my predicament, I told them that day that I never took their money but if their camera saw me making those changes with my own money, how will I defend myself?
Question number 2) Can I contest the amount? and if I end up paying them, will this show up on my record for future employers when they do a background check on me. What if I don't pay the settlement fee? I really need an urgent reply as the law firm told me that the fee will double if I do not respond as they sent me letters that I didn't receive.
I am really worried about this affecting me as I have big responsibilities. Thank you in advance!

You're probably in one of the super secret retail theft national databases.
You'll never know what they said about you, but your reputation is so soiled you'll likely never work in retail, or as a person trusted to handle money.
There are many threads similar to yours, search the forum for information.

You didn't have to defend yourself. They didn't care when they summoned you it was to get you to blab, and to tell you Trump's famous two word line: " You're fired!!!!!"

You can contest the $800, but they won't budge, except to double their demand.
This will hurt you and your family much more than 800 bucks.
You probably won't get unemployment, and you're likely to have a long dry spell seeking a good job.

Google the Internet, it hurts a lot of people, but so does stealing.

If a lawsuit has been filed, it is a simple matter to verify. The court will have a record and you will have to be served. I am leery of any lawyer who would call and offer to settle a claim for money when you aren't aware a claim has even been filed. It would be in your best interest to see a lawyer of your own. Consults are usually free and law school clinics and legal aid clinics can be lower cost options.

Are they offering to not file charges if you make restitution? If you go that route, I would want a signed agreement that lays out the terms of the payment (no lawsuit, nuetral reference, confidentiality, etc.). If you truly didn't take any money, you might be better off seeing if they do file a claim and fighting it. This is where a lawyer who actually has the facts and has talked to the lawyer from the employer is very useful. Your lawyer can then advise based on the facts of the case what is in your best interest. Were it me, I would not hand over $800 based on a letter from an attorney I never heard of with out some sort of assurance that paying will mean anything other than a smaller bank account.

Please tell me that you at least realize it was stupid to mix personal money and company money, especially without a witness and prior approval.

I work as a Retail theft consultant and advise parties like yourself or even retailer son various issues many similar to your own. You do not need to respond or act on any phone call. You do not know who this is or if they are indeed acting on behalf of your former employer. Until you are served or get a letter in mail saying you owe money they do not act. Make no admissions or even discuss your defense. Not all retailers subscribe to the databases mentioned earlier so its possible your name is not in there or that all potential employers can see it. If there is video of the money being taken you may video this video through "discovery" as well as any and all evidence against you. If you did not steal this may show your innocence. You need to talk to a Lawyer who can tell you your best course of action