You're absolutely right, Kendra! Pitch is only one component to the female voice. Unfortunately, thanks to nearly a century-old technology still in use, the phone kindly filters out all of that, laying bare the remnants of our male voices for all the world to hear.
I've tried to adjust my speech pattern when speaking on the phone to incorporate a more feminine variance in tone - mostly learned from observation. The resonance I can damp down to a degree but I find myself unconsciously straining those muscles when either on the phone or speaking to someone I don't really know that well. Of course, that turns my voice into a complete trainwreck but sometimes, just sometimes I can find that perfect blend of resonance and variance in pitch, and I get properly gendered over the phone.
It takes work! I don't mean that it takes practice, it still takes concentration. If I'm tired, I find myself lapsing into the old, flat, monotonous male speech patterns, albeit with a somewhat female-sounding voice.
I had a notion earlier in the week that I've been working the muscles in my throat so much in the last 18 months that I could probably crack walnuts with them at this point!
Get your beauty rest and keep at it! The only way we can get over these hurdles is to keep charging at them until they're finally behind us!