I shop there too.
One sunday I lost my cool and ruined one of their staffs Sunday. It made me realize what a dick I am complaining about garden furniture to someone who is just trying to make ends meet.
I no longer loose my cool.
I now watch other customers who feel it necessary to take out their bad mood/bad week or bad life out on a minimum wage employee.
They expect to receive treatment as if they are shopping at a boutique and not a hyper market.
I find it sad, especially cause half the time the customer is wrong and a dick who is trying to use “the customer is always right” as a way of bending the rules and making themselves feel better at the expense of others who are lower paid and just trying to make a living.

So in short get over yourself.