Amar Chitra Katha — Subscription not working after payment going through the app

I have subscribed for an yearly subscription on the ack comics app on my iphone. The payment has gone through, it’s showing that I have subscribed successfully. But I cannot get access to the content the app still. I tried calling the customer numbers available on their website but none of them go through. I have emailed them multiple times but have not received a reply yet. Kindly help me try to clear the issue.
Thank you.