foreighn sim

Hello,

I have an unlocked iphone ( bought in the netherlands but currently using a provider from belgium).. I’m staying in Bali, indonesia for a while so a bought a simcard.. with my two travelbuddies it works.. My phone immediately starts up as if you bought a new one and than it says “unvallid sim”.. I contacted my provider but they can’t do anything because the phone is purchased elsewhere..

any tips?

Greetings,

Nena