HappyEasyGo — Excess charges

I booked my flight through Happyeasygo from Bangalore to Lucknow on 25-Apr-2021. I asked them to reschedule flight flight due to the lockdown. They sent out the email that I can either reschedule through the airline website or the link they provided.
I searched that whole email and there was no link. I even asked for the link. Since I had only few hours to reschedule the flight. I rescheduled through Airline website (GoFirst). The flight was eventually cancelled by the airline and they refunded amount to the Happyeasygo.

When I reached out to HappyEasyGo, they said they will charge me the reschedule amount for the service I never took. I have all the emails to prove that they have charged unfairly.