Butty,
XtaticX is right. If you enter the Puk incorrectly 10 times you'll have to buy a new SIM * only the owner of the phone can get this.
For the security questions, it's a Pay as You go phone isn't it?? In that case the details dont' have to be regg'd at all.
It would prolly be anything from name 3 regular numbers you dial, when did you last put credit on your phone, or something like that.
If the owner regg'd the details, then it would be full name, address & postcode plus these days they add passwords to the account (which could be anything).
If I were you, I'd go to thew original owner & get the details then get them changed over hun.
Give me a call if you want any info...I'm surprised you didn't call me anyway for this one !!
