Disrespected by a store cashier

I just left the store now after an altercation I had with one of the female cashiers. I am so disappointed at the level of low client service standard I received. I was on the phone in the queue, looking at the cashier and waiting for her to call me. Then, I ask if I may come and she says yes. Then I ask her why she didn't call me and ahw says, I should have seen that I should come bcos she wasn't helping anyone. The level of disrespect was disgusting. Then I say to her, I thought she was busy ans didn't want to just come. She answers me still and says, busy with what cos I was on the phone. Please re train ur cashiers, cos therws no ways this is allowed