Have you ever tried to spell something over the phone and resorted to using words like “Banana” and “Paul” when someone couldn’t tell the difference between B or P? You probably then tried to continue to replace words with letters only to realize you have no idea how this alphabet works.
Military or navy call signs have been around since WWII. The most common version used today is the Standard NATO alphabet. These were designed to make sure there are no mistakes in a situation where communication is difficult, but you don’t need to wait for a disaster to learn the correct call signs.
All numbers are pronounced normally except 9 which is pronounced NIN-ER.