I remember having an Orange SIM that was pin locked years ago (like 2002ish -2009ish time I think) but had no idea what the pin was... Tried the 'default' options listed around the place but no joy so ended up getting PUK locked. Memory is a bit hazy but I think after some googling I found a sim serial number > PUK code calculator / list somewhere online which worked
. Probably not possible for newer SIM cards though I guess, Orange probably got hacked or used an unsecure algorithm for generating the codes or something. I guess (I'm 95% sure I never had to ring up customer services or whatever to get a code, as I don't think I even knew that was an option then, despite it being what everyone advises you to do now).
Anyway, since then I don't think any of my SIMs have come locked by default (or possibly came with a generic 0000 / 1234 code) and I never bothered setting a pin, because as my logic went there's no point risking the hassle of forgetting the PIN and getting locked out when I try to change phones in the future, and if my phone was stolen I'd be far more bothered by the loss of my phone than the loss of £10 or so of credit on my SIM card
. If a SIM pin is all that stands between me and my bank account getting pwned though I might have to rethink that...