That definitely sucks I know how you feel. In situations like this are you able to call the offenders out on their behaviour? Especially not letting you finish would be a good one since you could give immediate feedback that it is not okay. I have done this with my work boss and while difficult, it is important to communicate you do not like it and it needs to stop. I have never had anyone ask me if it was ok to talk over me while I stutter so unfortunately the burden falls on us.