Ms Smith was one of the winners for overall attitude, wow factor and professionalism.
She has worked at NZCU South for two and a-half years.
NZCU South chief executive Tania Dickie said she was delighted with the win.
''Antoinette is fantastic with customers. She goes out of her way to explain things in a way that is relevant to them.''
The credit union's contact centre was also a top three finalist in the banking category along with eventual winner Rabobank direct and ANZ.
It was the third year the credit union had entered the awards and the aim was to be a finalist.
''We are excited our team achieved success and met their goal,'' Ms Dickie said.
All NZCU South contact centre staff were involved in on-the-job coaching to ensure they provided the best service, she said.
The Dunedin-based contact centre employs 10 staff and services all of the South Island.
The credit union has total assets of more than $110 million, 21,000 members and 90 staff.
