Don't try to change your accent. The "country" sound is charming. :-)
In the business I'm in, I speak with folks all over the country, many of whom are extremely pompous. Some folks are quite nice about my southern accent, but some folks are so taken back, they can't mask their rudeness over it.
I've found that if I become quiet after an affront and let the silence fall like a rock, they get the hint.