if you are purchasing a SOHO (which is commercial based property) then yes, in fact, you are liable to pay these charges from the date you signed the sale and purchase agreement.

for residential units, you are required to pay maintenance charges IN ADVANCE (usually 4 months) prior to your collection of keys, these will be deducted through the next 4 months duration.

you can complain this to the developer but whatever it is, they are not giving you keys if you are not paying them that advance. it's sort of like buying a car, if you car has defects, you need to sort it out with the sales but you still have you service your car loan nonetheless.