ECS deduction without my knowledge, no reply by insurance company

The amount of Rs 6000 odd rupees are been deducted from my account for 2 consecutive years through ecs for the LIC premium with out my knowledge and mandatory instructions. When asked L.I.C they are putting the blame on the bank and the bank is putting the blame on the L.I.C. L.I.C when intimated through a email and even printout copy of the complain letter has not yet given the explanation yet, in fact I was been told by the LIC to give my account details or the authority to hand over my cheque of the amount to my agent and that also verbally and not in writing anywhere. I have asked from bank the NACH/ Mandate form as well on which signature of the person is required before allowing ECS but they are not providing it. How should i deal with this n how to stop further deduction from my account. Please help