Need some LEGAL advice on consumer rights/policy? Its very important. Please help!?

I took a pension policy from Aviva on Jan, 2009. My mode of payment was through ECS. I realized that my installment used to first credited and then debited back after 7 days to my bank account. I informed the same to them and they said it was some technical glitch in the system and will fix it within 10 days. Nothing happened and the case stretched for long three months with no clue what was the issue. Then in frustration I slammed the sales manager who came to my place for this policy. He in return again asked for 24 hours and then I came to know that there was issue with my ECS mandate. Some how the mandate did not reach my bank. There after I received a call from one of their reps as a payment reminder for my brother's policy. Then I inquired is it possible to make my payments using cheque till the time I work out the ESC thing with my bank and she said YES. She also informed me of their free service wherein their rep will come and collect the cheque from my place. I was kinda obliged as it was going to save my time so I said yes for the service. She also told me that the best feature of this service was that I will be getting my payment receipt then and there. Which I did but its been almost a month and they haven't yet credited my units to my policy account. This policy is directly linked to the market and the market keeps fluctuating. Who knows what NAVs will I be getting now. I have done almost everything I can from my side but they have been of no help. There is this 3 years locking period on this policy, meaning I cannot just end it or else I need to part with the amount that I have already paid. That means I'm left with no choice rather than just wait and keep taking their pathetic service. Its been a big pain in my a** from the day one. Now its been really too much and I want to teach some lesson so that they start taking things seriously and some poor customer doesn't have to go through all the hardships that I have been going. Is there any ground that I can sue this company. Please help!