I'm so sorry! As a native English speaker, even I can hear how easily someone could mix up "A" and "8"! Are the tests especially tricky? In a real conversation, you can ask for clarification - there is this thing called the NATO phonetic alphabet, and it means that, if you're unsure whether the speaker said "A" or "8", you can ask "A as in Adam?" or Alpha or whichever you prefer. You probably can't ask that during tests though.. A possible tip for your tests would be that "8" will never be in a surname, and "A" will never be in a telephone number - unless the speaker says a string of numbers and then a word with enough letters to complete the phone number. I don't know if Russian phones have letters on the keypad under each number, but American phones do. That would just be cruel, I think, but my older brother has a friend who used to tell people his phone number was "8-5-5 GOAT", which was easy to remember, and is why some people (but mostly companies) do it. The harderst part, I think, would be flight numbers, because they can contain letters or numbers. I guess you have to just listen for the "t" sound at the end of "8". It's the only difference in pronunciation, and is hardly ever dropped in American English. Good luck!