Not able to send AT command to sim module after converting aurdino to usb to ttl

I have aurdino omega328 and sim808 module.
I am trying to send drectly at commands to sim808 so I tried changing aurdino to USB to TTL

I put the RST to GND on aurdino
TX of aurdino to TX of sim module
RX of aurdino to RX of sim module

I opened serial monitor from aurdino Id and provided supply to sim module.
I can see module rdy written on serial monitor but when i send AT command, not output.

I tried changing following also but no luck
RX of aurdino to TX of sim module
TX of aurdino to RX of sim module

Attached pics of my connection

I wrote normal code in aurdino to send AT commands and read from serial port. I can see AT command output correctly, but usb to ttl no output.

following is code.

#include <SoftwareSerial.h>
SoftwareSerial mySerial(3,4);

void setup() {

void loop() {
if (mySerial.available()) {
if (Serial.available()) {