My mother is quite "dys-accent-al" (is there a word for that?). While there are a few accents she can manage quite well, she cannot understand anyone with an unfamiliar accent.
There is an ophthamologist in the same town who came from South Africa over 40 years ago and has the slightest "posh British" accent, but she can't understand most of what he says even though most of their conversations consist of eye exams - "is 1 better? or 2?", "what?", "1 or 2?", "what?", ...
A few weeks ago, she had to call Symantec's tech support line. The call took about two hours because the support rep had to spell a lot of words out a la "a as in apple, b as in banana, ..." after the first part of the conversation where they had to agree on the "alphabet"
Rep:"e as in eagle" (ih oz'n aygull)
Mom:"is that e as in egg? or a as in apple"
Rep:"e as in egg"
etc.