Should agency stop paying money?

He has been working for flexspecialisten for 6 years. Currently he has been working at G. in W. for 3 years. From January 1, the CAO in my company has changed. The agency reimbursed me for commuting costs of 5 euros per day. When the CAO changes, the agency should stop paying me this money and pay € 0.21 per kilometer. He still gets 25 euros a week and G. pays the agency 50 euros. I have been in contact with the coordinators for a month and have written to the office in person and have not received any response.
Please help me to solve this situation