funcion de Arduino IDE que manda un mqtt por SIM7080G requeire el topic y el mensaje

#include <Arduino.h>
  #include <SIM7080G.h>
  #include <WiFi.h> //Include the Wi-Fi library
  #include <PubSubClient.h>
  #include <string.h>

  char ssid[] = "my_wifi_name";
  char pass[] = "my_wifi_pass";
  char server[] = "mqtt.thingspeak.com";
  char topic[] = "channels/948297/publish/";
  char clientID[] = "clientID";
  char key[] = "A1DG0I9XWENHRXJL";
  char mensaje[] = "field1=10&field2=20";
  WiFiClient espClient;
  PubSubClient client(espClient);


  #define PIN_SIM_PWR_ON  34
  #define PIN_SIM_RESET  35
  #define PIN_SOCKET_TX  27
  #define PIN_SOCKET_RX  26