SCI Channel

You are not the one hundreth, much less the first, person to ask that, and I wouldn't be surprised if you aren't even the one thousandth.

Anyway, the answer is, no, you cannot just add a single channel, unless it's a premium channel like HBO. The main reason is, if every channel was offered separately, so few people would want most of them that they would have to raise their monthly rates to make enough money to stay in business, so chances are you would be paying just as much for it if it was separate as you would if it was part of a much larger package.