Banks
Aren't banks stupid?I changed address, so wrote to a savings account telling them to change it. A week later I can no longer access it over the phone (it is a phone account). I phone the helpline to find out why, and it is because they had problems recognising my signature so cancelled the phone access until I had phoned them to confirm that it was me who wanted to change my address.
I hadn't received a letter, so they sent it again. Then I called up and said "Yes, it's me". For security I had to tell them my balance. "But all my statements have gone to the old address, and you won't let me access the telephone account".
"You'd better write to us".