Have you reported the missing channels to Plex? This thread would be a good place to start:
Or you could go straight to creating your own thread, just ensure you give it the Live TV & DVR tag.
Either way, make sure to include as much detail as possible including the ZIP codes affected, the channels missing, their call signs and the expected network, if applicable.
Finally, have you tried some neighboring ZIP codes? I just did a quick test, and it looks like both 78209 and 78220 have 109 listings whereas 78210 only has 102 (for whatever reason). You may find that there are other ZIPs which are even more complete. At the very least you could use 78209 and have 7 additional listings.