Vodafone when you call for a billing query: “Please enter the 17 digit account number we gave you once, by email, three years ago into your telephone keypad.”
*jabs number into phone, pausing to memorise the next grouping about half way through*
“Sorry, that number is not recognised. We will now end the call”.
*many hours later when you finally get through*
“Hi. Can I start by taking your account number?”
Also WH Smith, because they’re backwards exploitative predatory price-fixing bastards.