Hi Rathy,
We get this error when any Field Symbol is not assigned correctly and we try to give some value to that variable.
if your statement I feel the issue is with
assign component P_CHA_CUSTOMER of structure C_S_DATA to <fs_customer>.
here P_CHA_CUSTOMER should be the field name of internal table C_S_DATA.
Can you confirm if P_CHA_CUSTOMER is field name?
Also look in ST22 on which exact line the dump is coming.
thanks,
Puneet