Despite a lot of flying, I've never had to call and request a change because the airline changed my flights so that my connecting flight departs about three hours before my first flight arrives. Is there a specific way to request help with this from Delta?

I'm flying SFO - BNA in March with a connection at LAX. Originally, the first flight departed SFO at 1pm. The second flight departed LAX at 5:40 pm. Now the first flight departs SFO at 12:26 pm while the LAX flight they've booked me into departs LAX at 10am. There is more than one flight with wide open seating in First (yes, I booked into First) that departs LAX after my now SFO flight arrives, so I'm not sure why they didn't switch me to one of those options.

I shouldn't have to pay anything additional to be switched to a flight that works, right?

Having said that, I could really use the help of a few specific phrases - like a script of sorts - to use when calling to explain my situation to request help. I'll spare you the long story, but I have issues conversing over the phone. Any help with key phrases or specific points to say would be greatly appreciated. Thank you.