3DS issue swap note


Koopa Troopa
I have a little issue. On swap note I can't use spotpass because of the age I suppose. However I own a used 3DS and I'm not sure if the previous owners entered an age below 18. I want to know if there is a way to change the age if this is the case. The only other thing I can think about is parental control but I don't want to do that... Help?
Letter Box should have nothing to do with Age Restrictions.
All you need to do, is:
1. Go to Letter Box.
2. Go to Settings.
3. Make sure everything is set on "Yes" or "On", as seen here:
Do you know the PIN Code of it?
If not, then only a Format can solve this problem.
I don't have parental controls set. When I change spotpass from no to yes it says "this feature allows you to share user generated content online that may include your personal information. Tap OK to go to system settings before starting this feature."
Then do whatever it says, I guess.
From this point, I don't know what to do, as I never had this.
There is no place you insert your age, just your Birthday (Day and Month).
If there is a Are Restriction, you should ask your seller for the PIN Code to Parental Control.