Sathya Agencies — Complaint against for purchases of laptop

Address: 100 ft road coimbatore

I am writing to formally raise a concern regarding the purchase of an HP laptop on 24/07/2025 from Sathya Agencies pvt ltd store located at No: 393, 394, Rajendra Prasad Road, Gandhipuram, 100ft Road, Coimbatore.
The payment was made as follows:
₹8, 663 through GPay (Transaction reference available upon request)
₹47, 837 through Bajaj Finance loan
Total paid: ₹56, 500

However, the online invoice I received was only for ₹53, 620 (Invoice #: 250012CBE2003721), not matching the amount I paid. Upon inquiry over phone, staff assured me that the remaining balance would be refunded within two days. As of today (01/08/2025), I have not received any refund.
Today, I visited directly in shop again to resolve the matter, but I was handed a new bill for ₹56, 000 (invoice #: 250012CBE2003905) which:
Does not match the actual product serial number: 5CD5111Q8Qof the HP laptop I purchased.
Raises concerns about potential misrepresentation or invoice manipulation.
I request that you:
Provide a correct bill matching the actual HP laptop I purchased, with accurate serial number and IMEI (if applicable).
Refund the excess amount if any discrepancy exists between the actual product value and the paid amount.