In line with the regulation imposed by the Ministry of Communication & Informatics, there’s no minimum age to sign up. During the registration, you will be asked to input your NIK and KK number. If you’re not 17 yet, you can input your NIK as stated in your KK. Make sure your full name and date of birth are the same as listed.
Please note that according to the rules of the Ministry of Communication and Informatics, one NIK can only be registered for three phone numbers under the same network - in this case, XL.