TV online through site or app and data usage

I've been told by sales people and the tech people that viewing shows with the Contour app or watching tv online through the https://watchtv.cox.com/ website will not use my Internet data but I can not find written confirmation of this.  Can you please provide written confirmation of this.  The main reason I went back to TV services is because I was reaching my monthly data usage limit and I don't want to go over by streaming content through the website or the contour app.  Is there an app for desktop use?