It is up to you and the client how long your conversation lasts. Your calls can exceed the time limit you set if you allow it, and you will be able to charge more in this case.
Each additional minute can be charged in proportion to the length of the meeting booked. (for example: if a 60-minute meeting was booked for a price of €60, then every additional minute will cost €1 ). If the call ends prematurely, the agreed unit length will still be charged, unless you decide to charge less. You have the possibility to change the rate at the end of the session if you choose to.