Bharat Sanchar Nigam [BSNL] — broadband billing related

Govt is implementing g. S. T from 1st july 2017. We the customer of bsnl broadband customer two bills for may & june. Generally the bill is generated either in 9th or 11th day of billing cycle and due date is for 30/31st of the month.in month of june they send a bill in june that is upto 25th. They are counting the next month bill from 26th june to 31st july eith new g. S, t rate for 35 days. How it can be possible. No hopeful solution is received on subsequent enquiry. Pl provide a solution. Contact no - [protected].