Receiving a gsm message and displaying it on lcd

I have looked at your code.
I think you are confused about what you need to do.
The exchange of messages with the modem is quite complicated.

As I said in my last post you need to understand how to put messages on the LCD.
You must practise this.

When that is done, you can move on to sending and receiving messages.

Don't use a modem, use your PC to send /receivie messages using a USB-serial converter.
Use a simple program such as "Terminal.exe" to send text.
When you can do that,let me know and we can work on SMS messages.