What's going on here? I suddenly received a reminder from Dayun Express today. I haven't bought anything online either. What's going on here?

First, see if the delivery address is your location, and then see if there are any relatives and friends you know at the delivery address. It's possible that relatives and friends told you only after they mailed the package to you. Just wait for the receipt after verifying this situation. If the receiving address does not match your city, it may be that the information was sent incorrectly. If there are no relatives and friends you know at the sending address, and the receiving address is indeed your city, it is likely that the network billing personnel used your address to make billing services and packages.