Have you received any memo from the bank informing you on some cheque being returned unpaid.If yes this memo will give the reason for return.
ECs return happens, if the balance in the concerned bank account is insufficient.
You have mentioned that the bank has levied charges for ECS return.Did you receive any info on this from the bank, e.g email, bank memo by courier.
If not then visit the bank, do not start a debate,tactfully collect copy of the bank statement, ECS/ Cheque return meme for your record.
If you have not signed or authorised any ECS from your bank account, point this out to the bank, and in case the bank informs you that they are in the possesion of some ECS authorisation by you, do not forget to obtain a copy of the same, without raising any debate.After having all these documents you shall be clear what has happenned.
If the bank has erred, the Branch Manager of the bank shall be happy to give you a waiver for Rs.276.00
Still if you are not satisfied you can persue for deficiency in service/unfair trade practice etc, however pls keep in mind the wise piece of advice from Mr.Gundlapallis.