How to make a complain about a dairy having poor customer care?

yeah, so from the topic but I am talking about New Zealand. Like, how to make a complaint to a New Zealand's government which's taking care of this? I've just experienced a worst customer care ever. The owner of this dairy just keep shouting at me just because I splattered a piece of chocolate on her mat! ? And, I spend like 10 dollars at least everyday at her shop so am having a big disappointment and want to make a complain somehow
 
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