Applicability of TDS

We have one most practicle issue regarding TDS., we are isuue the Sales Commission Debit note at once time, now that reverse by the benificiary by part amount due to commission amount raise on full value and part sales is return so benificiary now reverse the debit note to us  in part value of commission but we have already received the payment by them after deducted the TDS on the same., so what we can do if tds applicable amount is reversed now ? pleaase it's very helpful to us.