log in to your account then click on the "Plan and device".
This takes you to a page "My tariffs and devices" & "Manage my services" with Parental control is there.
Turn it OFF by moving the "switch" in your account.(Click the other side of the rectangle box).
Allow time for your account to update then reboot your phone.
If you want to say thanks > click 'Kudos'.Answered your question? > click 'Mark as Helpful Answer' also.