I found most videos on the internet and even the EVA voice app didn't help. And I've completely trained my voice.
This is the method I used:
You know that feeling you get when you swallow, when your throat moves up and everything. You want to hold that feeling. At first is a difficult thing to do, even breath, but the more you practice the easier it is to breathe. Once you can breathe then you can try to talk. It's a bit difficult at first, and you may only be able to do it for a few seconds, but once you can talk easily with it you can then go on to changing the pitch of your voice.
For me I did a do re me method. Using that scale, you want to go, "do, re, me, fa, so, la, ti," raising your voice higher each time. it's the "so, la, ti" that will be the base line for your voice. Once you can get that base down you can then go from there and go up higher if you don't think it sounds high enough. And then after a few months, you'll have mostly perfected it. Also never talk nasally because that really sounds bad and I've seen videos suggest doing that, but this method right here should bring you up to a female range and have you sounding 100% female even on the phone.
also here is a clip of my voice to show the results:
https://clyp.it/cthhmqm0I hope this helps ^_^ ~Scarlet