1. The common area maintenance charges may not be levied at the rates as applicable to other common areas especially when you have got exclusive terrace rights.
You may dispute it and ask them to give it in writing so that you can take the dispute through court of law.
2. How Society's maintenance has to be charged is explained in Part IX, Bye-laws 65 to 71 in the Bye-laws book of the year 2014.
If you find difficulties in your CHS charging its dues, then under the Bye-law No.172 make a complaint to your CHS quoting the relevant Bye-law/s.
If your CHS is not taking any action within 15 days of your complaint letter, then after giving a reminder complaint to your CHS, in which you will state that if CHS has not taken any action in another 15 days, and under Bye-law No. 174(A)(xii), you will make a complaint against your CHS to Deputy Registrar of Co-operative Societies.
If still no action is taken, then you will make complaint to Deputy Registrar, against your CHS, as stated above, with copy of your complaints to your CHS.