Don't feel bad about it, it's easy to not notice, with money going in and out all the time. i am sure they should have offered you an alternative way of paying over time, instead of just dipping into your account, at the end of the day it was their error.
And sending your details to an unknown is not on.....I have heard so many bad things about this bank, I would never have anything to do with them.

chin up babe