I know what you mean about Carrefours.
My OH and myself were waiting to pay at the checkout, last year, when my husband said that he felt ill. We had been waiting ages at the head of the queue to pay by credit card. Told the problem to the checkout girl in English (not sure why, but had presumed that they all spoke English!!!) and I got a very blank look.
Luckily, I can also speak Spanish!!
After repeating the problem, in Spanish, the girl rushed around with a chair for my husband - and even asked if he would like something to drink!!
Sometimes, the lingo comes in very handy!