Giant Eagle

I got a call from giant eagle loss prevention today. They stated that they needed to talk to me today or legal action was going to be taken and police would be involved.
On June 28th we made a purchase. Wanted it split on 2 debit cards. Went into a line with a cashier, so it was not self checkout. Cashier was told to put $100 on one card, which we ran. And the rest on another card which we ran as well. Transaction went through, but the cashiers' drawer popped open. He asked if we hit cash back. Said no. He gave the receipt and we left. Went there 5 more time since today. Apparently the cashier hit $100 in cash and his drawer was short, yet they were going to press charges of fraud against me! How is it my fault? Am I even responsible for the mistake? I'm not the one hitting the buttons!
I'm going to speak to the GM because with the way I was treated by their corporate loss prevention, I'm owed a huge apology from Giant Eagle. Thinking I stiffed them on purpose. Threatening me with sending cops to arrest me on fraud. I have one week to pay the $100. Makes my blood boil