Hi @Manuel Andrade, welcome to the forum! No worries, you can get a sim only package, however you will have to go to a KPN store for this. You will need one of the below listed forms of ID. And, take a look at this topic for more info about getting a contract without a Dutch ID. 

Accepted forms of ID are

• EU passport given out here in the Netherlands
• EU passport given out in another EU country
• Dutch driver's license
• Dutch ID
• Residency permit
• Diplomatic passport
• Residency permit W

In addition to this, persons without a Dutch ID need a BRP from the county hall.