To unlock use this guide Guide: Unlocking an O2 phone to use a different SIM card
To UnBLOCK your phone use this guide https://www.o2.co.uk/help/phones-sims-and-devices/unblock-your-phone
*The Game Is On*
Phone is hardlocked due to too many failed attempts at unlocking.
You now need an MCK from, I presume, Samsung?
I'll ask one of our community team to help.