Most Tv's will add channels without deleting the first channels that are selected and some Digital Tv's have the ability to add channels manually one at a time.
If adding channels manually one at a time , must add the Real Digital channel that is being transmitted and received.
Tvfool lists the Real channels and (Virt) virtual numbers.
The Real channel is what is added.
Here is a way to have more channels if the Tv will not add channels automaticly or manually one at a time.
A second Digital tuner.
http://www.epvision.com.
Channel Master Digital tuners ,
http://www.channelmasterstore.com.
These High Quality Digital Broadcast Tuners with DVR's are great for recording programs.