https://www.bbc.co.uk/news/business-44052530Pre-authorisation. In case you're not familiar with this, the seller of something that you want to buy (very often this is a hotel) will use your card details to Pre-authorise payment up to a certain amount. For example, you book a hotel room and you will pay upon departure, but you may also have a meal and run up a bar bill, so when you check in the hotel gets a Pre-authorisation code up to the maximum that they think you are likely to spend. You go to fill up, in the case below ASDA is getting pre-authorisation up to the maximum amount of fuel it thinks you are likely to buy. The card company or bank then works on the assumption that you may well actually spend that amount and of course it has guaranteed payment to the vendor.
All well and good, except that if every hotel, petrol station, or whatever that supplies something where the final bill is not known until after it has been supplied, it could end up that we can't buy enything as the credit limit or bank funds required would be impractical. Driving to Scotland and back from The South in a couple of days or so, with hotels and a couple of tankfulls may require a very healthy card limit or bank account.
A while ago I booked a holiday. The holiday company got pre-authorisation but didn't use it. Then I went to pay but the card was declined as I needed available funds for double the amount of the holiday. I see some angry voices and a lot of confusion if this becomes commonplace.
as I can't understand what they are saying 
. Not bad for being made to feel like a naughty schoolboy