Amendment in gstr1 already filed with more than 500 lines

Vipin (Accountant) (21 Points)

20 June 2019  

While filing GSTR1 of October 2018, I have wrongly uploaded the data of one of our sister concern which have more than 1500 line  items.  HOW can I amend the data and  its look like amendment  in portal is only possible for 500 lines.  I still had not filed the MArch return and waiting for a solution.