I didn't have the same experience at my last job as you are having but I know my speech kept me from ever advancing to a higher position in the company. Even tho I knew for a fact I was qualified and could do plenty of the higher paying jobs. I remember getting tested one day, having to talk on the walkie talkie, and I failed miserably. My boss asked me about speech therapy, blah blah, after that...I knew for sure I'd be stuck just driving a forklift forever with them. So, I had to deal with the reality of my situation, and luckily I got on at a much higher paying job, doing the same work. So, I don't even think about it now. I know it sucks, but you have to find another way around it, to get the money that you want. Even if that means changing careers or leaving the company.