First check
Confirm the payment was credited as principal part-prepayment rather than a future-instalment advance, and note the value date shown on the loan ledger.
What to do
Request the revised amortisation schedule and the product rule that determines EMI versus tenure recast. Compare principal immediately before and after the payment, then identify the first schedule line that does not reproduce.
Done when
The principal and revised schedule reflect the part-prepayment on the correct value date and the resulting EMI/tenure treatment matches the documented product rule or borrower instruction.
If it still fails
Raise the discrepancy with the lender using the payment reference, ledger and requested recast option. Keep normal undisputed instalments current while the schedule error is reviewed.