Hi @Stellakarypidou 

What kind of SIM card is it?

When starting a subscription you receive the SIM card via the Postal service. Separately you receive an e-mail with an activation code. Via the KPN website you can active the card by entering SIM card-number and activation code.  → https://mijn-bestelling.kpn.com/activatie/

Or is it a prepaid SIM card? This card will automatically activate by placing it in the phone and connecting to the KPN network in the Netherlands.

Hi @Stellakarypidou Did you manage to activate the sim with tips Ruud gave you?