A teenager must be at least 16 years old to have their own membership but a parent or guardian would have to sign off as the responsible party. Even if that teenager is paying the parent must still sign as the responsible party after the fact. If they are 18 years old then they can sign on their own accord. If parent is paying then the paying party just needs to sign as the account holder responsible for the payments each month.
Not sure you will need to call them.
Thanks! Your answer is awaiting moderation.