Annual service charge going up from £3300 to £5000

The property management are saying they need to build a pot because loads more work needs to be done on the building. The building is around 20 years old. But it's just getting unaffordable. When we moved here 4 years ago it was only £1400 a year, and it's just kept going up uncontrollably each year. One of our neighbours has been trying to sell for over a year too and said that no one will buy because of the insane service charge