SIM800L - ATD Works and Rings but will stop ringing after about 25 seconds


Newbie here.

So I managed to get the SIM800L working with the UNO WIFI Rev 2. It sends SMS and Dials etc.

I am using AT commands but I have a problem that when I init a call ATD the module will only ring the number for around 25 seconds and then timeouts.

Been trying to read the AT command book and I tried passing ATS7=50 but still does not work. Am i missing a particular AT command please?

I also tried to comment the ATH command and still times out. I am looking for a way on how to make it time out after 60 secs.

Any ideas what I am missing?

Thanks guys.

void callNumber(String phone_no)
    Serial.println("Calling the number " + String(phone_no));
    // mySerial.println("ATS7=50");
    // updateSerial();
    mySerial.println("ATD+ " + phone_no + ";"); //  change ZZ with country code and xxxxxxxxxxx with phone number to dial

    Serial.println("Call hang off");
    mySerial.println("ATH"); //hang up