Mcdonalds Did not give me a full cup of frappe. Columbus Ohio

I bought a large frappe and I told them the cup was nowhere close to full. They showed me a line that says ice and said thats were the cup is suppose to be filled to. I told them that line is to let them know that's where you're supposed to fill the ice up to, when your making the drink. That's why the line says ice. At $4 a cup it should be to the top of the cup. I even took a picture of our drinks. My husband got a strawberry smoothie and his was even less than mine and then there was a lady that walked by us that had a full cup. I go to the same McDonald's everyday and every day I have a full cup so why today is it different.