PhonePe — transaction and cashback

Website:

Phonepe and Myntra

I have made a transaction in myntra on 25th december, 2018 using phonepe payment app and paid through credit card.
Later i realised that there is no cash back and also not showing any transaction details either in myntra and phonepe transaction history.
I contacted first myntra and they said phonepe has to respond on the transaction. So i keep contacting them on support page and provided all required details except the transaction id, which i didn't capture it.
But these buggers keep copy paste the same reply saying that 'please provide transaction i'd and phonepe number...' don't these guys has any sense how they copy/paste the same reply multiple times.
Can't they track the transaction details when i have already provided my phonepe number. How to trust these kind of payment apps when they can't track a small transaction.
These phonepe guys really cheating the customer with improper applications and just trying to attract the customer by showing as some cashback etc.