Today, I received a short message from Hangzhou Post: You have a package, please call immediately to check it. Is it true?/You don't say. I haven't bought anything recently.

If it's a private mobile phone number, it's probably fake. This service is generally sent through the SMS platform. Of course, not all messages sent by SMS platforms are true. If it's the information of SMS platform, you might as well call the postal service to ask if they have this service and if the SMS number is theirs. It will be clear in the future. Don't call back directly if you don't know the situation. It may be phone fraud, or it may be waiting for you to call and ask you to do a series of operations to defraud your money.