Bad Attitude to Request for Service

I was waiting in a queue at Customer Service Rosebank Mall last week. Two cashiers were at tills. 5 additional staff were hovering about behind them. Very soon there were 7 customers in the queue. When the Supervisor came out to authorise a transaction I politely asked if she could open another till, given the large number of customers waiting & the 5 additional staff hovering about. The Supervisor glanced up at me (I was 2nd in the queue), gave NO verbal response, continued punching in at the till. She also ignored my second request. Only when I said that I was not being difficult but trying to speed things up given that she had so many staff, did she snap at me that nobody else could operate the tills, the 5 other staff were training. When I pointed out to her that the staff now wrapping a gift for a customer had previously been on a till, so could not a trainee wrap so she could come back to operate a till, she glared at me, said something undoubtedly rude to her colleague, completely ignored me and another customer who also spoke up, and disappeared back into her office. I reported this to floor management downstairs but doubt any action was taken. Pity I didn't get a name.