I put up my hand, feeling like a schoolgirl trying to get the teacher's attention.
Fortunately, the self-serve check-out's monitor bustled over and told me to look at the sticker on the apple.
"Of course!" I replied. "Silly of me!"
I returned to my task but then realised that I was using the supermarket bags and not the ones I bring myself to cut down on using plastic bags.
So I swapped them over.
All hell broke loose.
"You have removed an item from the bagging area!" the screen screamed and refused to continue checking out my food.
"Of course I have, in the interests of saving the environment you idiot," I said.
"Please consult the supervisor!" it said, followed by a loud beeping alarm.
Again, I was in school, in deep trouble and everyone knew it.
My "teacher" bustled over again, inserted a key and pressed a few buttons. 'Please continue," she commanded.
By the time I left the supermarket I had taken 15 minutes longer to purchase my food than I usually did and my blood pressure was through the roof.
The next time I attempted to do it was with my husband.
"Not that way, the other way. No, that way. Oh, just give it to me," I snapped as he attempted to scan the barcode on a packet of crackers.
"No, no, no ... like this," I continued. "Honestly, you have no idea."
We left barely talking to each other.
Self-serve seems like a great idea. It gives a customer the impression that they are in control of their own destiny. I can check out my own groceries, put my own petrol in my car and generate my own airline boarding pass. I must be in charge.
But behind self-serve is simply the ability of companies to get rid of staff. And it appears the whole exercise has been a bit of a disaster.
Petrol stations now provide a "forecourt concierge" to help us do the job we've been doing ourselves for years to make us feel valued. In England, Tescos has admitted that cutting costs by replacing people with machines hasn't worked and it will be recruiting 8000 new staff.
I haven't used a self-serve check-out for months in the hope that it may save someone their job. In return, I've learned that one check-out girl is an alcoholic, another is concerned about the effects of "local eating" on the economy of Zimbabwe and another never eats dates. And I've realised that extra five minutes in my daily routine is worth the wait.