KPN internet keeps freezing during work calls after switching from Ziggo

I have recently moved from Ziggo to KPN as internet provider.

When signing the contract, I explained that I work from home and that I really need stable connection due to the the constant calls I have every day. KPN promised their connection was very stable were very emphatic to say I would not notice any difference between Ziggo and KPN

Furthermore, they told me Fiber was going to be installed in my building soon, so I agreed with the offer. I COULD NOT REGRET THIS DECISION MORE.

The internet is insanely unstable, to the point I have to use my phone as a hotspot most days (thank god I have a vodafone phone, and not KPN). Since day one, I could not have ONE SINGLE CALL where the internet worked properly and I could hear the person without having one of more freezes in the call. It's frustrating and I cannot work like this. it's just a terrible product.

To make things worse, when the technician came to install my internet, he told me KPN has NO PLANNED DATE to bring fiber to my building yet. It's coming, but they don't know when. I asked for an estimate and he said if he had to guess, he'd say next year!!!

And as if this wasn't bad enough, I understood I was signing a 2-year subscription, but now I see in my plan that I have a 3-year contract. I literally cannot work with such poor internet!

What can I do to break this insane contract and go back to decent internet?