Customer services lied to me 3 times. It is in the records. I will take legal actions. I can not quit my subscription because of them!!

I started my one year subscription for KPN house internet at May 2023. In November, I moved my house and internet to a new address. I asked them if my contract end date will change or not. They told me that it will stay same. I called them 2-3 times just to clarify this. Each time, I have been informed that it will not change. 
Now, I would like to end my contract in May 2024. 2weeks ago, I called them and explained this story. They decided to change my end date to May 2024. I also saw it on the app. Later on, suddenly, my end date is changed back to December 2024 again!! Without even a notification or warning!!
Today, I called the customer services and they are now telling me that I need to stay with them untill November and there is nothing possible to do. They also told me that noone has the right to say that my end date was May 2024. They told me lies 3 times. I do not suggest this company to no one. Just use another provider because they have thrustworty customer service and willing to help. I regret the day I switched to KPN from Ziggo.
I have nothing to do but take also legal actions.