Flight 7989, service from PHX to OAK via LAX is a regular United Express flight. It's not uncommon for a carrier to have a "direct" flight via an intermediate location. In some cases there is a change of plane at the intermediate location too. According to the schedule, your flight would have had 52 minutes on the ground. If there was to be a change of plane, the Sky West people should have assisted you in quick transportation to your new aircraft.

If you do write United, keep in mind that all services provided to you were by Sky West. UAL had nothing to do with your experience that day. I am sure they will send your comments to Sky West, but expect that to result in some additional time to get a response.

If it is helpful, the contact information for Sky West is:

Customer Relations
444 South River Road
St. George, UT 84790
435-634-3400