Windcave would not respond to questions from the Herald about how many people were affected.
A spokesman for BNZ has confirmed all of the incorrect charges have been reversed.
Hunter received a refund on Thursday.
"No one would give me a straight answer, from the shop or from head office - it was all conflicting messages of what was going on.
"It was just a frustrating time for that sort of money to be taken out of your bank account this close to Christmas."
He said it would have been a miserable Christmas if the refund had not come back.
A spokeswoman for The Warehouse Group said: "There was an issue with Windcave, impacting BNZ customers on Saturday.
"As a result, there were erroneous charges made for some BNZ customers. These payments have been identified and the reversal process is taking place between Windcave and BNZ to reverse charges that were made in error. Refunds will be automatically applied by the payment provider. We apologise for any inconvenience to our customers."