Voice is a hard one. But also pretty important if you want to pass fully down the line.
There are really only a couple of options as other girls have mentioned. Surgery or training. I'll only talk about training...
Training takes a LONG time. I took about a year to get to a point where my voice passed consistently. And even now, I'm always fine tuning it and changing little things.

I tried DIY methods from the web, I tried coaching with Andrea James ( google her ), and finally coaching with a local voice therapist with almost 30 years experience with transwomen. Anyone in Melbourne is welcome to PM me for contact details.
Regardless of training approach, the aim is the same. However producing a female voice with a male voice box is hard. It has to be re-shaped, re-positioned, breathing has to be controlled, and the way you sound words has to change. There are muscles to learn to control that do all of that, and they need to be exercised to be of any use. If that sounds daunting, it should!
There are approaches that focus directly on the shape and position of your throat, and approaches that use other indirect, but more vocal methods, to teach the same thing. The later method is where I started, but it didn't work well for me. Once I started with the more direct methods ( forgetting speech and focusing on position and shape of my throat ), my voice improved dramatically.
And there's only an internet full of information with numerous different approaches.

Spend some time to see if any make sense to you.
What my voice therapist did for me was fantastic though. She helped me get the basics rights, and then move past the basics with skills not easily taught through other material. Such as modifying my resonance to make my voice carry, and a quality she called 'twang'. Those were all skills that built upon the voice I was still developing. More importantly, she was able to teach me and explain the physical changes happening to produce sounds. That's what worked for me with muscle memory etc.
My voice now is fantastic by my own high standard, and according to my former voice therapist. I've yet to be mis-gendered with it. And people who knew the old me and old voice are blown away. They say I sound like any other girl and would never be able to tell I was born male.
I guess the point with all of this... training can be so effective, but takes so much time and dedication while not knowing where the end is. But once learned, wow

. It's been the same with other transwomen I've met in person.

EDIT: I've come to find that a female singing voice is a totally different kettle of fish. Even with upper vocal range that rivals some cis women, it's so different. There so much to learn! From what I've read, it takes many years to develop, and may even be impossible for some voice boxes to produce a female singing voice. Of course that won't stop me from trying