When you have an upset stomach milk can help temporarily to fix an upset stomach but it only helps for around 20 to 30 minutes.
Drinking milk helps to relieve an upset stomach by temporarily coating the lining of your stomach which helps to buffer the stomach acid in your stomach.
That's what provides temporary relief from the upset stomach but it doesn't last long unless you drink more milk.
You can drink some ginger ale or add a few tablespoons of apple cider vinegar to a glass of water and drink it as I find that apple cider vinegar helps me when I have an upset stomach.
Or you can take some Pepto Bismol or drink some 7 Up or drink just plain water as it will hydrate you and make your upset stomach feel better.
You should also switch to a bland diet such as Bananas, Rice and Toast to help keep you full while settling the upset stomach.