Due date for filing GSTR1

But the portal showing 13/04/2019 as the last date!

If a dealer is filing quarterly return for 2018-19 by virtue of his 2017-18 turnover being less than 1.50 crores, and during the fourth quarter, his turnover has crossed 1.50 crores. But since he has already filed three quarterly returns, he can't change the quarterly option during the remaining part of the year, and so he has to file a quarterly return for the period Jan to Mar also. And accordingly, the due date in his case shall be 30th April'2019, despite his turnover having already crossed 1.50 Crores. 

However, for April'19 onward until June'19, he has to opt for, and file a monthly return. And for July onward, as the Council has already fixed new threshold of 5 Crores,so he would be given an option again to file quartely return. 

Raja Sir, please correct me if I am wrong. Regards.