Cashier couldnt assist and gave me bad attitude.

I went to Spar to buy a R10.00 airtime with a R100.00 note and she told me that she will give me the R90.00 coins, I asked her to ask another cashiers for a change, she gave me my money back and told me that its not her job to go and look for a change. She told me that its either I take my money back or I take coins and its not even her job to tell me what kind of a change she has on her till, she was only trying to make me a favour. Another cashier that was sitting next to her assisted me. It was the first time receiving a bad customer service like that in my life and I've worked with customers before and the way the lady treated me it made my whole day a disaster.