I often go to customer service and ask them to check me out. When they point to the self checkout, I tell them I prefer a human.

Never had any issues except one time I was at Lowe's and the woman just wouldn't do it. I had to tell her either check me out or agree that whatever I ring up is accurate.

She called a manager over it, who then checked me out.

I'm still bitter about it.

Then find somewhere else to buy your two things. I all but refuse to even go to the big box stores anymore.

Yup. Sorry. I to feel that pain. But it is either go to a different store (if one is available), be very careful, or deal with the police and judicial system.