Our units had a similar problem a few years ago, although we are a much smaller complex. One of the things our OC did was to get comparision levys/charges for other stratas. On that basis we went to the owners. We presented the owners with a comparision of what 4 other strata were being charged and that way we showed that what we were being charged wasn’t excessive.
Also ask for a copy of the contract this new Strata Manager wants you to sign, as we found that on comparing contracts the prices weren’t that different. Indeed some of the conditions the new SM wanted us to sign up to were quite constricting.