Phone required me to update my passcode from 4 to 6+ digits

Two days ago, I got on my phone in the I ring and it prompted me to update my passcode within 59 minutes. I read a few forums and all of them said to update the phone to make the prompt go away. I updated my IOS and the moment it finished, my phone prompted me again to update my code, but within the next 7 minutes. I waited until I had 3 minutes and reluctantly changed my code. It wouldn’t allow me to use a 4 digit code. I had to use 6 or more. How do I go back to a 4 digit code?!?!?!?!?