That is because you programmed the dvd recorder to change its channel from 3 to (whatever channel you wanted to record). All the channel changing should be done on the set top box from Verizon, not the dvd recorder. If you change the set top box to whatever channel it is that you want to record, and leave the settings for the dvd recorder to stay at channel 3, it should record fine.
The recorder has to be on channel 3 if you want to get the signal to come through. So for example, if you have something coming on at 8pm tonight on channel 75...setup the recording on the dvd recorder to record Channel 3 (because you don't want this to change) at 8pm but change the channel on the set top box (Verizon provided box) to channel 75.
Before we had to use set top boxes you could take that dvd recorder and plug it straight into the wall and use it like you were trying to. Unfortunately times are changing with the whole 'go digital' movement.