New install - trouble with External Prefix

Hi,
I am trying to use a carrier which needs a prefix passed before the number. But when I put in a prefix, Wazo always sends the number to the trunk without it, and also leaves the two-digit prefix on which I set for it to strip. Has anyone had this porblem?
Thanks,
Steve

EDIT: This is now working normally. Not sure what happened, but it started sending out the correct digits.