Standard Chartered Bank — not admitting their promise

my name is parvinder singh residing in Ludhiana.I m having a loan account with standard charted bank under the account no.47650125.in the month of june-10 i applied for loan closure,then i received a call from customer care and they asked me the reason why i want to close my loan account,i told them that i m offered by a bank the same loan @ 8.90 % fixed for the years where your is @ 9.25% varriable,then teny asked me to wait for 3-4 days so they can talk to their officers regarding the same.after that at the last week of the month of june-10 again i received the call from customer care and they said that they are also agree with the same rate of interest i.e 8.90% but i have to deposit the conversion fee RS.7500/- i said ok.after that i receive the letter for the same on the first week of july-10.then i went to the bank to deposit the same on 2nd week of july-10,bank said me to come after 2-3 days as they have to confirm it from their head office.again on 20.7.10 i went to the bank & bank authorities (after confirming from their head office) taken a cheque for Rs.7500 from me & assured me about the reducing the rae of interest from 9.25% to 8.90%.i m having the receipt for the same.
Now in the mid of august when i checked with the customer care i came to know that rate of interest was not reduced
.even i received a letter dt.18.8.10 that your rate of interest is going to increase from 1.09.10 from 9.25% to 10% i shocked to receive that letter.i again contact with the bank and told them the full story,and showed them all the relevent documets they also agreed then they checked with their head office and told me that this offer was valid till 30.7.10 then i told them it was in time i submitted the cheque on 20.7.10 for which i m having the receipt also but they said SORRY we didn't receive the same.i showed them receipt but they still not agreeing and refusing the same.on account of STANDARD CHARTED BANK'S negligence i m facing such A BIG problem.