As far as I know, the high leg should be on the far right socket of the meter, for metering and then should be on the center (B) phase of the service disconnect or panel.
A coffee shop you say?
This type service 240/120 ct is usualy found with 3 phase motor equipment and some lights.
Grfetwell nailed it, it would be the electricains fault judging from your post.
Dnk..........
