Is it permissible for us to change the timings of holidays with the knowledge of our administration, and what is the ruling on the salaries received if that is not permissible?

The actual times of malfunctions must be recorded, and they should not be altered, as that constitutes lying and deception towards the other company. The owners of the company must be prohibited from this deception, and if they do not desist, it is impermissible to obey them in participating in it, even if it leads to leaving the job. The salaries received are permissible if the employee performs his work in monitoring and reporting malfunctions. If altering the malfunction times results in harm to the other company, then these damages must be guaranteed, and you may seek recourse from your own company for what you have guaranteed.