Hi @Constantin Becheanu, welcome! Sorry to hear you're having problems activating your sim card. A prepaid sim can be activated by making a phone call or sending a text. But, you have to do this while in the Netherlands. Have you tried this? If it didn't work, or you are not currently in the Netherlands, we can help you.

Quickest way is calling 0800-0402 (free). Or we can help you here on the forum. In that case, fill in your forum profile with the phone number and the number of the sim card. Reply here when you've done so.