What does no mean?

There are some words that mean basically the same in all languages. Take the word "no" for example. Now there are different pronunciations or different spellings but they're all pretty similar, hard to not understand what it means. Especially after you've said it 3 or 4 times and declined an offer explaining why you declined it and starting your explanation with "No thanks". So why do you keep asking for the same thing. It's hard to fathom but it happened to me and resulted in me blocking the person. My first ever block. Well intentional block anyway. I have accidentally blocked a few in the heat of the moment. Amazing.