Recover excess tax paid due to demand for very old ay

I was expecting a refund for my tax filed for AY2014-15 this month, but I got a notice in return saying that my refund is adjusted against a demand for AY2008-09, and I owed some more after the adjustment. I got tensed on seeing this, and immediately made the payment of the remaining demand and interest online. The demand amounted to Rs.40000/- odd and the interest around Rs.10000/- odd. I moreover, logged into the income tax site, and saw the demand and submitted that I accepted the demand as I did not have info on such old AY of mine. I found and realised later that the demand was not correct as the CPC had failed to consider Rs.1lakh deduction under 80C, and also considered a capital loss of around Rs.6000 as a capital gain, and had unfairly raised the demand. I realise that I made the payment of Rs.50k now for AY2008-09 and also accepted the demand online in the IT website. Is there any way to recover this amount now? Is it possible to file rectification or any other means to clarify on the demand and get back the excess tax paid for that AY? It is such a huge amount, so I really want to see if I can get it back. Another factor is currently, I am in NRI status and out of country for a few months more, so any visit to IT dept is also ruled out. Please guide me if I can recover the excess tax paid for such an old AY more than 6 years back.