How to reply to the thank-you note sent by the man?

Your boyfriend called you like this to test your reaction. If you don't object to this name, it means that you have the possibility of further development. If you don't like the name, he can also be said to be joking with you, and it won't be too embarrassing. He has taken the first step, it depends on how you handle it. If you like him and want to develop further, you can reply to him. You're welcome, dear. If you don't like him and just want to be friends, you can say, be serious and don't shout. Of course, it depends on how you used to get along and what kind of development you will decide.