Bad service and attitude from trainee manager

I was standing in the queue, which was very long. Every queue in the store was running down the aisles. When I came close to the till to pay, the security came to me and said I can't pay at the till, as it's a SASSA payout till. The cashier started arguing, not friendly at all. Had a bad attitude from the start. I asked to speak to a manager, as the notice didn't state you couldn't pay for your groceries at the till. My fianc? then asked the security to take us to another till to pay, but he did not want to do that and was laughing. The trainee manager came, her name is Susan van Wyk, she did not say a word. While I was speaking to her, she just stared out in front of her and didn't even look at me while I was speaking. The cashier then just started to ring up my groceries and Susan walked away, without saying one word, not even hello. I work in the customer service industry as well and never have I experienced bad service like that. I even told the cashier, I'm paying by debit card and didn't need any of the sassa money for change, but she just gave me attitude from the start. If that person is going to be a store manager, she needs a lot of training on how to deal with customers.