I literally could not talk on the phone for years. Every time it rang I had a full blown panic attack. Desensitization is the key. I see you’re doing some practicing. Step it up a bit by calling a friends voicemail and say what you would say when answering the phone at work. Pretend the beep is you picking up the phone ( perfect way to practice a time constraint). I find a one or two beat pause before speaking helps me to start on a easy full breath Lather, rinse repeat. I does get better