I came in Qatar as a laborer but now am working as...

Dear Customer,                             
Thanks for joining and trusting us, much appreciated!

We would like to inform you that according to the Qatari Labor Law, it grants the employer the right to assign the worker with different job other the determined job if that assignation doesn’t affect on the worker wage.
Therefore if the employer assigned you to be a supervisor is not legal violation as the below article states:
Article (45)
An employer may not assign a worker to perform a work other than the work agreed upon, unless that is to prevent an accident or to repair the resulting or in the case of force majeure, with the worker giving the rights resulting therefrom.
The employer may assign the worker to work other than the agreed work, if it is temporary or if this work is not substantially different from the original work and does not involve ill-treatment of the worker and provided that the worker's wages are not reduced.

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