Byju's — Plan cancellation - no proper response

We took a product in the mid of may this year and since our child is not responding well we cancelled the subscription within 14 days. Since i cancelled it i didn't put any amount in the bank accout. But byjus support team took 10 days to respond on this and by this time the ecs was hit and i had to face bounce charges for two time of rs.1200/-.
The question is why should we face bounce charges if the service is slow from their side? Even after many calls there is assurance that the charges will be refunded, but nothing happened.
There is no proper link between finance dept. And byjus team. The finance team kept calling us everyday though we cancelled it. Eventually we had to face the bounce charges for which their slow service is the reason.