Your channels 11 and 21 are not my channels 11 and 21. I have no idea where you are, who your service provider is, anything.
I do know that where I live, I keep getting annoying messages across the bottom of my screen on two of the four local channels that broadcast over the air. They are part of my cable package. These two channels are involved in a contract dispute with one of the competing satellite providers, either Direct TV or Dish, and customers of whichever company it is have lost those two channels until the dispute gets settled. The local channels want more money and Direct TV/Dish doesn't want to pay it.
The message these local channels are running is pointless, because they are telling affected customers to complain to their service provider, and those customers can't see the message because they aren't getting those channels.
So, complain to your service provider, see what the problem is. If they tell you they are having a dispute with the local channels, tell them that you want a credit on your bill for every day you haven't gotten those channels. Threaten to dump their service and try to get something out of them, free movie channels for three months, something. Because until they start paying the local channels again - the old contracts are ended and new ones must be entered into - you won't be getting those channels unless you put up an antenna - like the old days - and watch TV on those channels, the old way. You will have to unhook form your provider temporarily to watch them.