Can I use this as evidence to fire employees by SMS?

It can only be used as auxiliary evidence, and the valid document is the Certificate of Termination of Labor Contract or the dismissal document. If the employing unit fails to issue relevant supporting documents, it shall complain to the labor inspection.

Labor Contract Law

Article 50 When the employer dissolves or terminates the labor contract, it shall issue a certificate of dissolution or termination of the labor contract, and handle the transfer formalities of the file and social insurance relationship for the employee within 15 days.

Laborers shall handle the work handover according to the agreement of both parties. If the employing unit should pay economic compensation to the workers in accordance with the relevant provisions of this law, it should pay it when the work handover is completed.

The employing unit shall keep the text of the dissolved or terminated labor contract for at least two years for future reference.

Article 89 If an employer violates the provisions of this Law and fails to issue a written certificate to the laborer to dissolve or terminate the labor contract, the labor administrative department shall order it to make corrections; If it causes damage to workers, it shall be liable for compensation.