['I went to the grocery store and I had to bag my own groceries.', "Well that's pretty annoying. Aren't they supposed to have people there who do that for you?", "Yeah, that's what I thought.  It was quite irritating."]
If that happens again, you should tell them they should have to pay you the appropriate wage to do work that they're supposed to be doing themselves. That's insane!
I went to the grocery store and I had to bag my own groceries.  It was quite irritating.