asking for dues when emi is cleared

Dear Sir / Madame,
I had taken an ac from bajaj finance as details
NAME
NASREEN HUSSAIN
Mailing Address
37 B SAHMSUL HUDA ROAD BECK BAGAN KOLKATA 700017
Customer ID
3800961
Branch
KOLKATA
Product
CONSUMER DURABLE
Linked Agreement No.

Asset Description
SAMSUN-AC/AW182WA
Total Loans
1
No.Of Active Loans
1
No.Of Closed Loans
0
Mobile
8013629349
EmailId
[email protected]
Loan Purpose

LOAN ACCOUNT STATEMENT FOR 4100CD00077264
LOAN DETAILS
Loan Amount
16,200.00
ROI
0.00%
Tenure
12
EMI Received
10,800.00
Last Disbursal Date
12/07/2010
First Due Date
05/08/2010
End Installment Date
05/03/2011
Advance Instl.Amount/Number
5,400.00/4
Status
Active
Future Installment Amount
0.00
Future Installment Number
0
Future Principal Component
0.00
Future Interest Component
0.00
Fee Charge
0
Subvention Charge
0

I had missed two instalments and had paid the respective EMI via cash which is shown in the account but the payment bouncing fees was waived off by the person who came to collect the cash of the emi missed by me.
Now after two years they are again claiming the amount of cheque bouncing fees of Rs 700. why should i be duped when i was assured by the cash collector of my cheque bouncing fees being waived off.
Kindly looki into this matter thanking you
Regards
nasreen