Totally agree with Mr. Sumit.
It is held by various Courts that the disallowance would not attract where payments are made for different expenditure (different bills). Below is the gist of some of the decisions;
Provisions does not say that the aggreate of the amount should not exceed Rs. 2,500 (Now Rs.20,000). The words used are "in a sum", i.e., single sum has been used. Therefore, irrespective of any number of transactions, where the amount does not exceed Rs. 2,500 in each transaction, the rigours of Section 40A(3) will not apply. CIT v. Triveniprasad Pannalal [1997] 94 Taxman 381 (MP)./CIT v. Kothari Sanitation & Tiles (P.) Ltd. [2006] 282 ITR 117 (Mad.).