Scammers are calling potential victims and claiming to be from Visa, asking them if they have authorized a payment of £900? The scammers then ask their potential victims to go to the App Store and download AnyDesk, (this is a legitimate app that allows people access to your device), so they can remotely prevent hackers from using their cards.
But, credit card companies or banks will never call and ask you to download an app or other software.
Remember, never give your personal information, credit card information or account credentials to anyone who calls you unexpectedly claiming to be from your bank or credit card company.
If in doubt about a call, hangup and call your bank directly or whoever directly.