Are security locks per phone or sim cards?

I have an old phone that I don't use anymore but I use the same sim card for a new phone(v3 razor) that has been used before by another person with a different sim card. If I want to reset security codes, etc. is it something that takes effect on the phone or the sim card? So basically, if someone else sets passwords on a phone with a different sim card, do I have to know the old passwords to set my own passwords on the same phone but different sim card?

Are security locks per phone or sim cards?
Yes you need to know the passwords because it's through the phones security settings
Reply:Through the phone.