Essentially, this boils down to: Zone 9 (Xi'an) First, obtain a deregistration certificate. Then, ask them to issue a proof of retaining the existing call sign and authorizing its use in a different location. Bring this proof to Zone 4 to apply for a new license. When filling out the application, select "no" at the call sign application section, and enter your original call sign in the original call sign assignment section. Also submit the certificate obtained from Zone 9, informing them that you intend to continue using your previous call sign.
Here are two important points to remember:
Firstly, after obtaining the certificate from District 9, it is essential to make a color scan of it. This is because you might need it later, and if you hand over the original, it could create problems if you need it again in the future.
Secondly, I only communicated with the monitoring station two days ago. Now, all new applications/extensions/changes to licenses must be uploaded to the national system. This is a nationwide network, and information can also be accessed from other provinces.