That’s never happened to me before and it shouldn’t happen to anyone, so I’m really sorry that’s happened to you OP I’d email them and explain that you have a stutter and if they refuse to call back/accommodate you, that’s discriminating against a disability which is breaking the law (at least it is where I live) If you explain it and they still don’t come back to you, then you should feel sorry for them because they’d have lost out on a great candidate because of their own small mindedness and trust me, you don’t want to work for a company like that I’m sure you when you explain everything that it’ll be all good and you’ll get the chance you deserve. Keep your head up, OP 😊