Should I speak with an attorney about my District manager and the store I work for?

I work for a sales company, that sells cell phones out of a retail store. I have a kiosk in which I process my orders, but go to their cash register to ring up the phones after we process the order for the guest to pay for the phone. My district manager only comes by once in a while, and doesn't know much about what goes on. My district manager came in yesterday, and lectured me on our sales and how they should be better and asked a series of questions about the insurance to see how knowledgeable I was on it. We then moved on to another topic. She asked me if I had done something dishonest or that could potentially get me fired. I replied "No... why?" She then told me she has seen a video of me ringing up a guest, and pocketing their 100 dollar visa gift card. I explained she must have missed something. I said "I have never stolen anything in my life! It was probably when a guest purchased one to pay for their deposit at my computer online and I took it over to my computer for them." She replied "don't lie to me, I have seen the video and I know you took it!" I told her "I WOULD LIKE TO SEE THIS VIDEO!" in a blunt tone. She said " it isn't necessary and ***** has asked me not to say anything about it." I then told her " but it is necessary because I'm being accused for stealing when I don't and would never steal!" She then brought up another incident where I price matched two cell phones $30 off. Which I then replied that I asked my manager before doing it! And she told me I have to have a manager to assist me at doing that at all times. After a lecture and making me feel like a thief she left. She did this in front of employees and guests in the store in the open. In a normal tone of voice where every one could hear and embarrassed me really bad. I'm so ashamed even though I didn't do anything I feel like they look at me like a thief and a liar. I probably lost customers. What do I do? What CAN I do? Thank you.