Late reply on this — have you see the iOS 17 Accessibility feature “Personal Voice”? This is what you’re looking for. You can be on a normal phone call and type in responses to be said in (basically) your voice. I agree with other earlier comments of you should power through and develop your own fluency if you can. Years ago my job required me to be on the phone a lot. I would be okay once the call got going but I would often stutter on just saying “hello”. If I stuttered or blocked on the opening I would suck on the rest of the call. I had a music soundboard and recorded “hello” and a couple other opening phrases to start the call off for me. Personal Voice can do these things for you all in-device now.