Consumer Redressal

Hi respected sir/ma\'m, Actually dear I have a education loan from SBI ,which was sectioned by SBI LAUNDI (Branch code:2873) in 2008 , and from 2012 I started to pay my loan(5000 p/month). But from the beginning to till now they are charging same interest on original principal amount even my total amount has reduced.I complaint so many times in branch and SBI customer care department and also I have forwarded a written compliant to SBI head office Bhopal and RBI Bhopal(Complaint Number: 201314004001889) regarding that issue, But any body is not ready to take any action and not able to provide any kind of resolution. Please suggest me to do any thing as I have tried all possible ways whatever I could. Thanks