Won't send SMS

I'm trying to get the TEL0124  to send an sms according to the documents

The Red led Is  on

The blue blinks

I have the 2 jumpers set to D7/ D8

I have an external Battery  connected

When I upload the code nothing happens besides

Sketch uses 5094 bytes (2%) of program storage space. Maximum is 253952 bytes.
Global variables use 194 bytes (2%) of dynamic memory, leaving 7998 bytes for local variables. Maximum is 8192 bytes.

Code

#include <SoftwareSerial.h>
SoftwareSerial SIM7600(8, 7); // RX, TX

void setup() {

SIM7600.begin(9600);

delay(3000);

sendSMS("+41796855225", "Hello from Arduino!");

}

void loop() {

// Empty loop, SMS sent in setup()

}

void sendSMS(String number, String message) {

SIM7600.println("AT+CMGF=1"); // Set to text mode

delay(100);

SIM7600.println("AT+CMGS=\"" + number + "\""); // Set number to send SMS

delay(100);

SIM7600.println(message + "\r"); // Send message

delay(100);

SIM7600.println((char)26); // Send CTRL+Z to end SMS

delay(1000);

}