Hi Gopal,
First check whether you are really getting 500 char from gateway.
If no define table parameter as text so that you can get as many many char data you can in the same. And do the same process which you are doing using loop data.
If yes Calculate length of the string.
Split you data with 132 char length and pass to the FM which you are using. and append values into the table. Once you get all the text use FM 'SAVE_TEXT' if text already exits or use FM .'CREATE_TEXT' if text does not exits. Use 'COMMIT_TEXT' at end to confirm
Santosh