Wages
The terms of employment, like wages and working hours, are agreed upon in the collective agreement. The wages must be at least as high as agreed in the collective agreement. They may be higher but never lower. Check that your wages are in accordance with the collective agreement.
Check with your representative or the people in the local PAM office whether your terms of employment are in accordance with the collective agreement.
What does my payslip tell me?
Do you know how to interpret the information given in your payslip? If the answer is no, it's worth to visit the online payslip with explanations included.
How to read a payslip?