Hark Infratech's maintenance charges are highway robbery!

I'm so frustrated with Hark Infratech Developers Pvt Ltd. We booked a flat in their Sector 5 project thinking it would be a good, low-maintenance option after the kids have moved out and we're selling our bigger house. The brochure said one thing, but the actual maintenance charges are insane! It's almost double what they initially quoted. Honestly not sure how they get away with this. It's eating into our retirement savings, matlab what's the point of downsizing? I'm paying almost the same as I was in the big house. Anyone else facing this with Hark Infratech? Is there anything we can do as residents to fight this? Should I just sell and move again? This is a nightmare. I feel totally cheated. What am I missing? Is this normal?