What shall we do when our employer compels us to...

If you work overtime, the employer is obligated to pay you in lieu of the overtime hours, which will be calculated as follows:
1) If you worked overtime on your regular workday, he is obligated to pay you a wage equivalent to 125% of your regular hourly wage.
2) If you worked overtime on a day off, he is obligated to pay you a wage equivalent to 150% of your regular hourly wage.
And if he refuses to pay you in lieu of overtime, you can either file a complaint against him with the labor office or file a lawsuit with the court