If you see any cancelled calls in the reports or the call history you don't need to worry about it.
Cancelled calls are not related to any issues with the service nor issues with the agents answering the calls.
When a customer or lead calls you there is a ringing period before the call is connected and starts ringing the agents. You will see the calls with the cancelled status when the people that call you cancel/hang up the phone before this period in which the call is connected and rings to the toky agent.
So if you see a cancelled call it means that the customer cancelled the call before your agent could answer it.
If you have any questions or concerns about this please reach out to email@example.com or send us a message on the chat.