Female Voice

It is advisable to practice your feminine voice if you are going to be out in public and intend to pass. It won’t matter how well you are dressed and how good you look if you start to speak with a deep masculine voice you will be given away instantly.
It is advisable to get a professional voice coach to help learn how to retrain your voice as there are many areas that are covered including:
PITCH
RESONANCE
DYNAMIC RANGE
ENUNCIATION
VOCABULARY
GRAMMAR

If you are not currently in a position to hire a voice coach there are a few things that you could try that may help:
Speak a little quieter than normal as this may help your voice sound softer.
Do not rush your words, speak a little slower.
Try and practice your ‘singsong’ voice. This is the voice you will quite often hear a trained telephonist use. When finishing each sentence the slightly raise the note of the last word which gives the sentence a ‘singsong’ sound.