HDFC Bank — ach debit return charges

I have visited the branch to check on why is hdfc charging debit return charges for my account when m paying my loan amount from amazon pay later on time. The branch staff had confirmed me that the charges are from amazpn pay later side. When i checked with amazon pay later team they gave me the statement and confirmed that the they have not charged any return charges. When i checked my last 6months statement. I have noticed that HDFC has debit almost 4000rs from my account inspite me paying my installments on time.
I want an immediate refund for the ACH debit returns.
My contact detail [protected].

Thanks
Rohini