Put A Security Code On Your Sim?

[Jennykenny]

I have a four digit code to start my 4s iPhone, for security, in case it is stolen.
Now read somewhere that I should have a code number on my Sim. How on earth would I do that??

[Milvus]

Instructions here JK
https://support.apple.com/en-gb/HT201529

[Jennykenny]

Thank you Milvus, but can't find the link to Sim Pin, on my phone.

[Jennykenny]

Sorry, take it back. Was looking under mobile instead of phone.

[Jennykenny]

Tried two attempts but it wouldn't allow me.
Give up.

[Milvus]

Did it give you a keypad to enter the pin?