Terrible picture

My picture scrambles,pixelates.freezes and shows newer frames over old ones.Couple months now. All 3 TVs.Replaced box,restarted,and all the other usual stuff.Had tech come out,seemed quite knowledgeable and thorough. Went over all hardware inside and out.Installed some kind of new grounded connection in the box on the back of the house. Said "give it a week". Well it's been more than that and they told us to get a wireless box.Sent me an Xi6-A box.Hooked it up and same problem started occurring within 1 minute.We had a problem years back and was told it was "noise in the lines",meaning the lines on the poles. Fixed it that time.Paying nearly $4,000 dollars a year for all my services and can't get a good picture.