My session was less than 15 mins, but I was charged for 15 mins.
Codementor charges a minimum of 15 minutes of a mentor's rate for each paid session, as mentioned on the confirmation screen before you enter the session room. This is to help make requests more worthwhile, as there may be requests that mentors can quickly resolve.
If this is an invalid session due to technical issues, you may ask your mentor to refund the session. For more help, please contact support.