He said a new security guard on duty that day was unaware of the bank's full guidelines regarding headwear.
The incident was a "genuine human error" and not intended to offend.
For security and identification reasons, ANZ staff or security guards could ask customers to remove head coverings and sunglasses.
"An important part of our guidelines and training, however, is to instruct staff to use their own discretion and judgment, taking into account religious and cultural issues, when asking a customer to remove any headgear. I appreciate this situation could have been managed differently and we apologise again for any offence," Belleher said.
Samuels said he accepted the apology in good faith and on behalf of all New Zealanders who had been asked to remove their head apparel.
He'd been into the same branch many times before with a pōtae so the incident was "bizarre".
He didn't even have to take off his hat to be identified when he went through airport security a few days earlier.
"All the same, if you're asked nicely to remove your hat and given a reason, I don't believe anyone would refuse," Samuels said.
Race Relations Commissioner Meng Foon also weighed into the pōtae incident at the time, saying if banks allowed other cultural garments to be worn, such as hijab and turbans, their position towards kaumātua could be discriminatory.
Foon said kaumātua often wore hats where he grew up on the East Coast.
"People need to be safe to speak their language, adorn their cultural dress and wear what is correct for their culture," he said.
Foon accepted there were security reasons for removing hats, but companies like ANZ needed processes in place to assess situations.
It is not the first time Samuels has gone into battle for his hat.
As a Labour MP from 1996-2008, he fought for the right to wear a pōtae in Parliament.
He has since been followed by other notable hat-wearers such as Te Paati Māori co-leader Rawiri Waititi, whose fondness for cowboy headgear is well known.