It looks like the bank made the error and it is up to them to sort it out, you shouldn't have to contact the guy to ask for the return of the money.
Unless of course you weren't clear in your instructions to the customer service official over the phone? When you say 'I usually say', does this mean you may not have been clear in your instructions?
The fact that you have been doing it 'for months' should be in your favour.
In future, I would advise that you get internet banking set up or else pay by direct debit/standing order/over the counter lodgement etc. so that you protect yourself against 'human error'.