HappyEasyGo — I am waiting for my refund since 76 day

I booked a flight from happy easy go, and due to some reasons I had to cancelled my flight, I cancelled my booking on 1st Dec, now it's been 76 day and did not received my refund amount yet.
I mailed to [protected]@happyeasygo.com for this case then they asked for refund later, I provided them the same. Now they are asking for stampcopy of airline, where would I found this. I called on there customer care and after listening my concern they just muted the call I waited for 10 minutes but no reply. What should I do?
My happy easy go order id:[protected]