SIM808 HTTP POST request

Hey guys,

I've got an DFRobot SIM808 Shield up and running with the GET example from their library:
click me

Now I need to post some sensor data to a server and I am trying to get a POST request running.
But it's not working. I guess there is something wrong with my chars "http_cmd" or "payload".

Could someone please help me with that?

Thank you! =)

#include <DFRobot_sim808.h>

#define APN "internet.telekom"
#define BN "telekom"
#define PW "telekom"

DFRobot_SIM808 sim808(&Serial);

char http_cmd[] = "POST /t/p9msd-1524305850/post HTTP/1.1\r\n\r\n";
char payload[] = "{Name:Alfred&Age:29}";
char buffer[512];

void setup(){
  //mySerial.begin(9600);
  Serial.begin(9600);
  
  //******** Initialize sim808 module *************
  while(!sim808.init()) {
      delay(1000);
      Serial.print("Sim808 init error\r\n");
  }
  delay(3000);  
    
  //*********** Attempt DHCP *******************
  while(!sim808.join(F(APN), F(BN), F(PW))) {
      Serial.println("Sim808 join network error");
      delay(2000);
  }

  //************ Successful DHCP ****************
  Serial.print("IP Address is ");
  Serial.println(sim808.getIPAddress());

  //*********** Establish a TCP connection ************
  if(!sim808.connect(TCP,"ptsv2.com", 80)) {
      Serial.println("Connect error");
  }else{
      Serial.println("Connect to server success");
  }

  //*********** Send a GET request *****************
  Serial.println("waiting to fetch...");
  sim808.send(http_cmd, sizeof(http_cmd)-1);
  sim808.send(payload, sizeof(payload)-1);
  while (true) {
      int ret = sim808.recv(buffer, sizeof(buffer)-1);
      if (ret <= 0){
          Serial.println("fetch over...");
          break; 
      }
      buffer[ret] = '\0';
      Serial.print("Recv: ");
      Serial.print(ret);
      Serial.print(" bytes: ");
      Serial.println(buffer);
      break;
  }

  //************* Close TCP or UDP connections **********
  sim808.close();

  //*** Disconnect wireless connection, Close Moving Scene *******
  sim808.disconnect();
}

void loop(){

}