Luckily, it's quite inexpensive to do, but it takes time and commitment. If you follow the information below and practice carefully for a few months, you will have a passable voice for the mere cost of a tape recorder. Everything I know is outlined below. The rest is up to you. Voice, another spectrum Vocal expression, like gender expression, is a spectrum.
Voices can have male or female characteristics, some physical, some behavioral.
Female voices come in a wide range which partially overlaps with male range. If you have enough feminine characteristics to offset the masculine characteristics, you will pass. It's that simple. You will probably never eliminate all of the masculine cues in your voice, but if your voice presents as overwhelmingly feminine, you'll do fine. Some of you will think all of this information is total overkill, but if you are having problems getting clocked because of your voice, understanding the absolute basics is vital to fixing that.