Fenesta Windows — Upvc window installation

Website:

www.fenesta.com

I have recently had pvc windows fitted in my home. I thought fenesta is a reputed company or so it says on their website. A couple of mm out is understandable, 4 inches out by measurement is seriously unprofessional. And that too after measurements were taken twice.
They insist on payment in advance too.
So i am left with a 4 inch gap between top beam and window.
If you are thinking fenesta windows. Think again!