HDFC Bank — excess emi receiver

Address: Ludhiana, Punjab

I had vehicle loan in hdfc. You charge 25 emi instead of 24 with extra penalty by saying that i have default in payment. But my bank sbi says that there is no default in any emi even my bank statement shows the same. I have files complaint in bank. They said they will refund money in 15 days but after 25 days still i have not recieved the money. Can you please suggest me how i can get the higher authority no. Otherwise i will sue in court