code: public VoiceCallResponse sendVoiceCall(final VoiceCall voiceCall) throws UnauthorizedException, GeneralException {
          if (voiceCall.getSource() == null) {
              throw new IllegalArgumentException("Source of voice call must be specified.");
          }
          if (voiceCall.getDestination() == null) {
              throw new IllegalArgumentException("Destination of voice call must be specified.");
          }
          if (voiceCall.getCallFlow() == null) {
              throw new IllegalArgumentException("Call flow of voice call must be specified.");
          }
  
          String url = String.format("%s%s", VOICE_CALLS_BASE_URL, VOICECALLSPATH);
  
          return messageBirdService.sendPayLoad(url, voiceCall, VoiceCallResponse.class);
      }
docs: Function for voice call to a number
  
  @param voiceCall Voice call object
  @return VoiceCallResponse
  @throws UnauthorizedException if client is unauthorized
  @throws GeneralException      general exception