15 items or less

I've been working at a grocery store for the past five years, so I've pretty much dealt with people being rude to me almost everyday within those five years, but the other day, I had a customer cussing at me for actually doing my job.   I told her I was on the  15 items or less lane and she would need to go on a regular lane on her next visit. This was after I had simultaneously finished scanning her 40+ items and given her a receipt. Apparently I was a  lazy cashier and I didn't wanna do my "fckn" job. How unbelievable is that?! You never really know what you;re gonna get next when working with customers.