Good morning Khan Academy users help team

Recently, I have shared a link that give access to my khan Academy account. And I would like to  change the view or  the link format that was giving access to other people without my consent. How do I make that ?  Is it possible to change the link format every time we want and prevent it from easily accessible to the people we shared before   ?  Your reply  would possibly help in any account like this.  Secondly, how do we get in touch with  instructors, tutors or   volunteers at Khan  Academy  when we encounter challenges   and remain unsolved  for some days  ? 

Thank you for your  reply and would like to thank you in advance for your time.