You should re-start Chabla application normally and make calls again, this should repair most of the potential problems. If the problem continues, do try to reboot your phone and then start Chabla again. If this does not help, contact Chabla support (Chabla>profile> Help>Submit request).
We are monitoring the Chabla and its functionalities continuously and most likely are already aware that your Chabla crashed. Mobile networks and connections are by far the most common source of problem in making calls, not the application itself.