NEED HELP

I NEED TO FIND CABLE MICRO USB(SMARTPHONE) TO Serial Communication(RX/TX) TO SEND SMS WITH
arduino MEGA 1280

Stop SHOUTING.

You can't connect usb directly to the Arduino's serial pins.

SO HOW CAN I CONECT MY SMARTPHONE TO THE TX/RX AND NOT WITH BT

Is your shift key or caps lock key stuck?

Which smart phone do you have?

ANDROID PHONE SGS

Seriously, quit with the BLOCK CAPITALS.

You could use a USB host shield, and the Android ADK.