Dollar General review: Unethical behavior

I went into the dollar general this first day of January and gathered $56.00 worth of products. The woman there had told me that I needed to used the self checkout in previous visits. I checked out all of my products and then scanned the hard copy coupon for $5.00 off. The register only took off $1.85.
The other woman who was stocking product near the self-checkout, came over and read me the sign that said, "This register does not take digital coupons. If you have a digital coupon use the other registers." She called up the other lady, who also felt in neccessary to read me the sign. I told her I could read and had already had the sign read to me. MY problem is I did not use a digital coupon. I used a coupon I had in my hand which is NOT a digital coupon. I didn't say anything, just asked to be checked out on another register.
At which point I was treated very rudely and told to leave. I think your customers deserve better service than this.