Guys, the solution has been posted already, see https://eu.community.samsung.com/t5/Galaxy-S9-S9/S9-region-lock-SIM-network-PIN-blocked/m-p/623124#M....
Your local Samsung service centre can help you with region locks and give you the required code if you forgot to make the 5 minutes phones using a local sim card in the country you bought your phone. The problem you have is that your phone is network locked, not region locked.
Different issue altogether.
As far as I know, this lock is imposed by the country where you want to use the phone, in my case Colombia. The only way to unblock my phone was to use an online unblocking service. I used UnlockBoot (https://store.unlockboot.com/). This worked perfectly. My phone was unblocked and I was then able to register my phone in Colombia without any problems.
It may cost you up to USD 50 but your expensive new phone will no longer be worthless!