So I've been on T just over 5 months now and pass 95-100% of the time in person but hardly ever on the phone (I did pass this morning though which was awesome). My voice has dropped significantly too. Maybe it's inflections in my voice, I dunno. I'm an admin assistant at a law firm and I'm the one answering the phone most of the time. I'm trying to make my phone voice more monotone but I think I answer too cheerfully, lol. Any advice guys?

That probably is it - too cheerful.  My therapist, also an FtM, had a tendancy to leave voicemails for me with a "sing-song" voice that I would have read as female.  Someone must have mentioned it to him (I never did) because the voicemails aren't "sing-song" anymore, definitely male sounding.

I've been passing very well on the phone for the last couple of months.  I really think that keeping it brief and just being polite is the key. 

Be friendly and courteous but not to courteous!  Being to courteous, i.e. saying thank you constantly and catering to them, is female conditioning, not male.  That will tip you off every time.  It took me a while to stop saying thank you at every little thing. 

The below is how NOT to do it. 

Telemarketer:  How are you today?

Me:  I'm good, thank you.

Telemarketer:  No, thank you!  We've been monitoring your phone calls because we are creeps and want to figure out ways to make you sign up for more services you don't need.

Me:  Wow, thank you for all your hard work.

Telemarketer:  uh, Your Welcome.  So do you want to sign up for our deluxe streaming movie package that only works between the hours of 2 and 4 AM?

Me:  Um, no Thank You not right now.  Money is really tight otherwise I would .... Perhaps some time in the future if you want to call back ... I'm sorry ...

Telemarketer:  Not a problem.  It was a pleasure to serve you today, ma'am.   

Bad, bad, bad.  This is how I do it now after much practice. 

Telemarketer:  How are you today?

Me:  I'm doing fine.

Telemarketer:  Glad to hear it.   We've been monitoring your phone calls because we are creeps and want to figure out ways to make you sign up for more services you don't need.

Me:  That does sound creepy.  I'm happy with the services I have now.

Telemarketer:  So glad to hear it once again.  So do you want to sign up for our deluxe streaming movie package that only works between the hours of 2 and 4 AM?

Me:  Like I said I'm happy with the service that I currently have. 

Telemarketer:  Please enjoy your day, Sir.  Thank you for your time.

Me: Goodbye   

It still seems slightly rude not saying thank you but no one seems to mind.  Being confident in yourself and your position goes a long way.  You don't need to work to please anyone else, especially when they are the ones calling and pestering you.