How to connect SIM800C to Arduino Mega?

I have the SIM800C module shown in the attached photo, and I have an Arduino Mega. I just want to be able to send messages and do GET commands. My problem is simple: I have no idea how to connect it to the Mega. What I’ve tried is:

SIM800C → Arduino Mega
5V → 5V (I’ve also tried connecting the module to a phone charger, 5V & 2A)
V_TTL → 5V (also have tried connecting it to the phone charger)
GND (just the one in the same side as the 5V) → GND
TXD → RX2
RXD → TX2

But I can’t get it to answer to AT commands. My code:

char c;

void setup() { 
  Serial.begin(9600); //Serial Monitor
  Serial2.begin(9600); //SIM800C
  delay(7000);
  Serial.println("SIM800C Test");
} 
 
void loop() {
  while (Serial2.available()) {
    c = Serial2.read();
    Serial.print(c);
  }

  while (Serial.available()) {
    c = Serial.read();
    if (c == '>') {
      //To send "CTRL+Z" after sending a text
      Serial2.println((char)26);
    } else {
      Serial2.write(c);
    }
  }
}

Does anyone know the proper way to connect the module to the Arduino?