Unlock code not working

[Kezman]

I have been trying to put a different sim in my galaxy s9 and said 'SIM network PIN blocked. Enter SIM network PUK'. The 8 digit unlatch code that O2 gave me doesn't work. Message says 'network unlock request unsuccessful'. Help!

[Edit: topic title clarified]

[Bambino]

@Kezman Please see this: https://www.o2.co.uk/help/phones-sims-and-devices/unblock-your-phone