Error: "Sim not provisioned"

Hi @Athanasios Siganos! Welcome to the KPN forum. 

Would you verify for me that it's a KPN number you are talking about? If it's the mobile number in your profile, this is an old KPN prepaid number. It has been deactivated some time ago because it has not been used. 

To keep a prepaid number active, it has to be used every now and again. You can do this by making a paid call or text or upgrading your prepaid. If you don't do this for a number of months you will get a warning that in time the card will be deactivated. If you don't respond to this the card will be deactivated. After this the mobile phone number will be eventually redistributed and can not be recovered. 

If your number was in service with a company other than KPN, please contact them. If it was a different number than the one in your profile, please update it there and let us know here. 

If it was the number in your profile, I`m sorry to say it can not be recovered.