Proof gathering

I took a Mutual Fund from a renounced financial institute and gave standing instructions to deduct on a monthly basis. They were however deducting once a few months without even informing. After multiple oral complaints, they totally stopped deducting since last April (2016). The amount was 12K per month. I nearly forgot about the whole Mutual Fund thing. Now suddenly after 12 months, they deducted 1,44,000 INR from my account - which is equal to 12 months of EMI. This was done without any notice, which made me run from pillar to post to identify who withdrew this amount. Now: - I've asked my bank to furnish the details of how this transaction carried out without my consent. - I've asked the financial institute on how they decided to withdraw INR 1,44,000 from my account without notifying me. I am so frustrated with both my bank - for not consulting me before completing the transaction, and the financial institute - that chose to arbitrarily withdraw such huge amount without notifying me. Is there anything that I need to do to gather more information for legal purposes in case I want to file a case against both of them? Please assist.