Owner does not want to pay the service cost settlement?

I have been renting my apartment from a housing company. Since November 2019. Every month I pay them an advance for utility costs, and they calculate the settlement once a year. This year, for the settlement for 2022, they calculated that I used more than 8000 kWh of electricity. I asked for clarification and detailed meter readings to prove this. Turns out that there were no regular meter readings done, and I have been overcharged by the not just for 2022, but for 2020 and 2021 too. They admitted their mistake and recalculated my yearly usage. According to their numbers, they owe me about €1200. But they refuse to pay, saying they need to settle it with the electricity company first. This has been going on for months. So in short, they admitted that they need to adjust the bills, but they refuse to pay what they owe. I sent them letters that I will involve the Huurcommissie and even start debt collection proceedings with lawyers if I have to. They always responded with a very vague answer and did not settle what they owe. What can I do in this situation? Thank you so much for your help!