Xfinity on demand

I recently start having this error code vm-16 when I try to access on demand since Monday. Long story short, comcast was contacted, they trouble shoot and sent signal blahs blah blah, end result was to get new box because old box not working and problem in my area Tamarac Fl. New box arrived 9/4 Wednesday, still not working. Tech came out 9/5 thursday and said it was fix? Watch on demand thursday night all night. Now this evening 9/6 friday night On demand is not working...what is going on and yall have nerve to call me today for survey of technician who came out and said I will be charge $70 visit and suggest to add HD for 9.95 monthly which I did. All the tech said is that my tv not compatible and I need high definition. guidelines>.