Received a text message from the birthday housekeeper. I've never used it. How did they know my name and birthday?

You never use it to mean that people around you don't use it. Your friend recorded your birthday with a birthday housekeeper, and then authorized the short message, so there will be these messages in the cloud. But only last name, birthday and mobile phone number, there is nothing to worry about. At the beginning of this year, when you go out to make a drip and pay by WeChat, others will know your name and phone number. Just ask people around you and you will know your date of birth. In contrast, it is more important to protect privacy such as self-passwords.