I’ve always been told that unless you get confirmation that your boss has seen your message or got your call then you continue until they do. Next time if you don’t have your managers work phone the workplace directly and ask to speak to them or get the information to contact them.

That being said if you are 17 you shouldn’t be the one expected to be responsible for delivering training to new employees and no matter your age your boss should be respectful. They can direct you to policy if you haven’t done it correctly but talking down to someone is not the way.

Half the battle is companies are switching everything digital. In my work we have three different apps, email and a company phone to communicate with each other and it is super confusing to keep in contact with each other as you have to check them all and information can be missed.