Hello ,
In the above call method in exporting
i_structure name = 'TESTING_TABLE'
method will pick the column name from structure field's itself, if want to change the the column name then you need to overwrite the existing column like below code.
example:
READ TABLE lt_fieldcatalog ASSIGNING <ls_fieldcatalog> WITH KEY fieldname = 'NETWR'.
IF sy-subrc eq 0.
<ls_fieldcatalog>-scrtext_s = 'Pos. Net worth'.
<ls_fieldcatalog>-scrtext_m = 'Pos. Net worth'.
<ls_fieldcatalog>-scrtext_l = 'Pos. Net worth'.
<ls_fieldcatalog>-reptext = <ls_fieldcatalog>-scrtext_s. " it will be displayed in the alv output
endif.