SIM800L not responding to AT commands

Projects Networking, Protocols, and Devices
1

I am using SIM800L (SimCom) with the Arduino UNO to send and receive sms. SIM800L module is getting connected to the network (LED is blinking every 3 sec) but not responding to any of the AT commands sent through arduino. I have used the following:
18650 Li-ion battery (3.7-4.2 V) for SIM800L
Stepped down the logic level of arduino to 3.3v using voltage divider
I folllowed the tutorial : In-Depth: Send Receive SMS & Call with SIM800L GSM Module & Arduino to make the connections.

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I dumped the basic AT commands testing code:

#include <SoftwareSerial.h>

//Create software serial object to communicate with SIM800L
SoftwareSerial mySerial(3, 2); //SIM800L Tx & Rx is connected to Arduino #3 & #2

void setup()
{
  //Begin serial communication with Arduino and Arduino IDE (Serial Monitor)
  Serial.begin(9600);
  
  //Begin serial communication with Arduino and SIM800L
  mySerial.begin(9600);

  Serial.println("Initializing...");
  delay(1000);

  mySerial.println("AT"); //Once the handshake test is successful, it will back to OK
  updateSerial();
  mySerial.println("AT+CSQ"); //Signal quality test, value range is 0-31 , 31 is the best
  updateSerial();
  mySerial.println("AT+CCID"); //Read SIM information to confirm whether the SIM is plugged
  updateSerial();
  mySerial.println("AT+CREG?"); //Check whether it has registered in the network
  updateSerial();
}

void loop()
{
  updateSerial();
}

void updateSerial()
{
  delay(500);
  while (Serial.available()) 
  {
    mySerial.write(Serial.read());//Forward what Serial received to Software Serial Port
  }
  while(mySerial.available()) 
  {
    Serial.write(mySerial.read());//Forward what Software Serial received to Serial Port
  }
}
2

If the network connection is established, what AT settings do you want to change?

3

There is a possibility that your Arduino doesn't detect the messages received because the output of the sim800l isn't in 5v logic.

You should try to add a level converter to go from 3.7V (your battery level) to 5V logic. You can use transistor for this stuff or buy a module already working.

Also, I remember using a sim800l, the default baudrate was supposed to be 9600bps, but mine was set on 19200bps. So you can try all the baudrate you have in case adding the level shifting didn't do the trick

Ofc, I assume your wiring is good. But if need you can send a pic to check it