Dear …
RE: Account __(Name and Reference#)__
Please allow this letter to serve as our formal request to __(name of organization)__ for a lower rate of interest on our __(type account)__.
__(name of Company) has been a customer of __(name of organization)__ for __(#)__ years now. In addition to being a loyal customer, we have proven that we are an excellent credit risk. We ensure that our payments are consistently made on time and are always current with our credit obligations.
For all these reasons, we believe that a lower rate for our account with your __(organization/firm/company)__ is justified. Thank you for your consideration of our request and we look forward to hearing from you soon.
Sincerely,