Hathway — Bill invoice showing incorrect amount

I had got a call from Hathway in May 2021 saying my account is due for renewal so I asked for monthly plan as I had 3 months plan earlier. Executive asked me to recharge prepaid account for Rs 607 and then he activated the monthly plan. However next month June 2021 I got a message to renew the plan which was supposed to expire. This time amount was Rs 589 and same was for July 2021. However when I checked the invoice in portal, for May 2021 amount shown is Rs 557 instead of Rs 607. Also it shows they reduced subscription charge of Rs 26.99 from actual billing amount and after adding GST, I had paid Rs 557. I dropped mail to Hathway billing desk pune to clarify about the same, however they are not responding with satisfactory answer. Also when I recharge online I got some receipt which shows Rs 607 paid, but the invoice in portal shows Rs 557 paid. I am not sure why I have paid Rs 50 more. I have attached both invoices for month of May 2021.