電話で”Bye”と言われたときの答え方って英語でなんて言うの？

Goodbye is a general of bidding farewell - it is suitable for both formal an informal situations. "Bye" is more informal, so that would be appropriate for situations with friends. But it isn't wrong to use it in formal situations, especially when you're very familiar with the person. "Cheers"is used mostly for informal situation. E.g. Cheers buddy, I'll talk to you tomorrow. E.g. I'll see you at the meeting tomorrow boss. Goodbye.

For friends, you can say "Talk to you later" Or even more simply "Later." This just means you will talk to them again maybe the next day or at a later date. For a boss, business colleague, or someone you do not know, you should say "Bye," "Goodbye," or "Have a nice day." Goodbye or Bye are the most common, but it is polite to wish some "Have a nice day."

Talk to you later. Bye. It was nice talking to you. Goodbye. Thank you. Bye. Yes you say it differently to a boss, co-worker, or a friend. For a boss you can say, "Goodbye", "Yes, I will get back to you later", "I will get on that. Bye". For a close friend you can say, "Love ya, bye", "later", "back atcha". For children it is cute to say, "later alligator", "after while crocodile".

If you want to respond to someone at the end of a phone call, you could use either the first or second example in an informal call - or, in the case of a colleague or even a boss, the third example has two parts: a positive parting message, and a farewell.

When talking to a boss or in any formal situation I would probably stick to 'goodbye' or 'bye'. Whereas, when talking to a friend I would say 'see ya' or 'catch you later' which simply means see you later.

When talking to a friend then you could say 'speak soon' or 'speak later' When talking to your colleagues/boss then you can use 'bye ' or 'goodbye'