i’ve learned at work especially on the phone to speak firmly and confidently and my stutter goes away. Not all the time especially if it’s an elder and I have to repeat myself then it comes back. At that point I just take a breath and start again with the same confident attitude I had before. (I work in a pharmacy) I doubt your voice sounds bad!! I will say too that starting new jobs my stutter was always worse but then as I grew comfortable it lessens however there are days when I warn everyone around me “just a heads up I got little sleep and running on caffeine and adderall so Imma be a stuttering mess today!!” and they’re genuinely good with speaking for me if I’m having issues with customers 😂🥰