Serve Legal -Tesco

This sounds really odd but I'm so nervous to ask people for ID. In my old job at a garage, I had loads of comments made about how I look underage etc and I know this sounds completely bonkers that I'm worrying about it as I'm 20. I currently work in Tesco who operate a Serve Legal policy which is where you ID anyone under the age of 25 as a precaution. However, the first time I tried it I had abuse hurled in my face and not only that I look 'underage' was made fun of but I had ' your bubbly personality should pop like a balloon cause you're a &***' was a bit extreme but made me feel like I literally dont want to serve anymore. It has really knocked my confidence. Does anyone have any advice as to what I can say to my manager for guidance and support? The MAIN question I wanted to ask was does anyone know if theres any additional training we can go on in this area?

Been shouted at, Screamed at, Punched, Had Ribena threw in my face for questioning peoples ages. Just keep a straight face and say you won't be served unless you can provide ID. Any person with sense would carry ID if they were buying age restricted products