I got "m'am" a few days ago on the phone too. I had a cold and was more nasal and had less voice control too though, so I just thought it was funny. Like you, Dominick, if I focus on how I'm speaking my voice is more masculine. I wouldn't say I'm forcing it lower, just concentrating on where I'm speaking from (chest mostly) so that I have less tendency to squeak or crack on upward inflections, if any.
My ex still gets "m'am" on the phone occasionally, and he's a 29 year old completely heterosexual cis-male. Some guys just have higher voices, but it's way too early in the game to assume that your voice will always be one of them. I've seen videos of transguys on Youtube who's voices took 2 years or more to fully drop, everyone's different man!