I received a verification code on SMS these two days, saying that this verification code is only used for WeChat account complaints. What is this?

There are three possibilities for this situation:

The first one is that when someone enters their own number to get the verification code, they make an error because their number is similar to yours.

Second, someone else used your number before, and it was bound to WeChat. Later, the number was changed, and it was not unbound. When the other party complains to the micro-signal, the system sends a series of verification codes to the number you are using by default because the number is not unbound.

Third, your micro-signal encounters hacking or trojans.