Wanneer krijg ik het teveel betaalde bedrag op mijn factuur terug?

Goodnight.
I hereby ask what has happened to the amount I have paid in excess since July 2023. Knowing that the contract states the amount of €25.01, I have been paying €35.99 every month until December. The situation was only resolved in January 2024, I had to go to the store several times to resolve the situation. The value is more than €10.98. We are talking about 6 months paying this extra amount, which in total amounts to €65.88.
I am attaching the contract with the actual values.
I would like to know how this situation will be resolved.
Thanks
I look forward to responding as soon as possible
Compliments
Jorge Mendonça