Unfortunately, no such feature is available at the moment, and it is not possible to implement it until tomorrow with TRB142 or other Teltonika device.
If that would be enough, as an alternative, you could try using Over IP mode of RS232 configuration, to establish TCP connection with the program on the customer's PC. Otherwise, if the call is a mandatory part of the process and data is transmitted through the call, it is not possible.
Such a feature would require additional development, and for that you would need to contact your local Teltonika sales representative.
Apologies for the inconvenience.