i hate it sometimes when someone calls me ''mate''

I hate that expression especially when you are talking to a business on the phone about purchasing a product, if the salesperson calls me mate - I tell this person I am not your mate and due to you being unprofessional I will shop at another store and left feedback on your webpage

It's an Australian thing. It's like the Americanism when calling everyone Buddy or Pal. And it means nothing. It's just slang people from Australia use when they don't know your name.

Yeah, I know what you mean. I feel the same when strangers call me darling, love, dear or dearie.
It's so obviously fake that I can't help wondering whether they're being patronising or deliberately sarcastic. Either way, I think it's just plain rude. However, I give them an equally fake response by remaining polite until the interaction is over. It's usually shop clerks - so fortunately, all I need do is avoid that shop in future.