That's not a problem. Personally, I believe that changing your call sign without authorization is equivalent to revoking the administrative permit (or amending it). Revoking an administrative permit requires following Article 69 of the Administrative Permit Law.
If any of the following situations occur, the administrative agency or its superior administrative agency that makes the administrative permit decision may revoke the administrative permit upon request from interested parties or based on their authority:
(1) When an employee of the administrative agency abuses their power or neglects their duties and makes a decision to grant the administrative permit;
(2) When the administrative agency exceeds its legal authority and makes a decision to grant the administrative permit;
(3) When the administrative agency violates the legal procedures and makes a decision to grant the administrative permit;
(4) When the administrative agency grants an administrative permit to an applicant who does not meet the eligibility requirements or does not comply with the legal conditions;
(5) Other situations where the administrative permit can be revoked according to law.
If a person obtains an administrative permit through fraudulent, corrupt, or other improper means, it should be revoked. If the revocation of an administrative permit under the provisions of paragraphs (1) and (2) causes significant harm to public interests, it will not be revoked. If the revocation of an administrative permit under paragraph (1) of this article causes damage to the legitimate rights and interests of the person granted the permit, the administrative agency shall compensate them in accordance with the law. If the revocation of an administrative permit under paragraph (2) of this article is carried out, the benefits obtained by the person granted the permit will not be protected.
I recommend that you request a written response from the administrative agency regarding the change (revocation) and have it mailed to you. If the administrative agency sends a document stating that they have revoked the administrative permit, you can then apply for judicial review or file a lawsuit against this administrative action.
I believe that such WeChat notifications have no legal effect.
There is a legal issue here. If the first license was not (legally) revoked, and then a second license was sent, what should the administrative party consider? Should they believe that they have obtained two completely different administrative permits (i.e., the administrative party uses both call signs for this equipment), or something else?