Read the small print in the contract you signed.

It seems to me that you had a trail 'free' period, which required you to actually cancel the contract at the end of the 'free' period.

If you didn't cancel the contract, then how can it be the responsibility of the dealers?

You should really try to do this via written correspondence rather than wasting hours on the phone, you will then have proper evidence to further your case. Telephone records often disappear.

i had opted for there months (Unlimited Usage) service of internet for which i had to pay complete charges in advance.after three months the service automatically stopped and even i was not interested in continuing the service.now after 6months the dealers are asking fr money for last six months and reasoning it as "i did not send them mail for cancellation of the services.so i will have to pay the charges for the service which is still active". what should i do ?