Hello Siddhi
There is not much we can help here. The yearly GA subscription, even pad in monthly installments, has a contracutal minimum duration of 6 months; it is clearly stated in the contract that you have signed; it can only be cancelled for the first time after 6 months. There is the GA monthly travel card which is valid for one month, without subscription, but has nothing to do with the GA yearly subscription paid in monthly installments for which you apparently signed up.
I think my answer is the same you were given by the helpline.
Best regards,
Roland