Many of my customer could not understand a word I said,but I could not understand them either.I have had to slow down my speach a lot.
when I was in the army and I was posted to england as an instructor I had to learn to slow down my speech very fast, as no one I was instructing could understand me, it was never a problem in my regiment as we were all from the same area
when I got married my wife had big problems being understood in Colchester, I told het to talk to them like they were thick and slow right down, that seemed to work, the funniest thing I seen though was when we moved back to scotland and she stood at the counter doing her best "talk to them like they are thick accent" and I was like FFS she is scottish just ask her for what you want