Did you have TV service before the contract tech arrived? Did you and the tech check TV service after he replaced parts on the outside? If yes, was it working?
Some time ago, a contract tech disconnected the outside splitter to my bedroom mini-box while trying to fix an issue with my Contour receiver. I didn't realize he'd done that until after he was gone. Since then, after a tech performs any maintenance, I always ask him to stick around until I've checked TV service on all TVs and checked my Internet and phone service.
The email to cox.help@cox.com is a good idea. You need to request a tech check your signal strength, including at the tap. It's best if that test occurs as close to the time of day as possible when you are experiencing the TV issue.