I have found that for most channels, I can successfully change closed caption (CC) font and background preferences (e.g., size color, font style) to meet my viewing needs. However, my preferred settings have never worked with a few channels I frequently watch (e.g., USA, NBCPhiladelphia SportsNet). I have this issue on both the SD and HD versions of these channels. [Coincidentally(?), both are owned by NBC Comcast; however, I don't have this issue on other NBC Comcast channels I watch like NBC and SyFy.]
This is problematic/annoying because the default captions are large and the background is solid black, which often blocks out meaningful parts of the screen. For example, for certain sporting events, the captions cover the running box score if the latter appears in the upper-left hand part of the screen.
Also puzzling—and possibly related—is that sometimes (but not often) on these channels, the closed captions within a commercial do conform to my CC preferences, but revert back to the default as soon as the scheduled program resumes.
Although I generally use the CC1 setting, I have tried CC2-CC6. While these options seem to work fine on most channels, they do not work at all on the problem channels, where CC1 is the only option I can use.
It is possible the CC issue exists on some of the hundreds of other channels I do not generally watch, but I'm not quite ready to troubleshoot the issue at this level. 
I have searched the Verizon Support site—and the web—for possible solutions, but I haven't even found another instance of this particular problem. I'd appreciate it if anyone has experienced this issue responds. I'd also appreciate any suggestions for troubleshooting that I haven't yet tried. Thanks in advance.