Metlife's COLA recalculation cut my payments with no explanation why

Are you aware of any class action lawsuits against Metlife Disability over their COLA adjustment method of calculations and application Of COLA? MetLife contacted me this year, after being on LTD since 2007, and eligible for annual Cola adjustments up to 3% based on SSA prior year cpi, since 2010. They claim that for 10 years they have overpaid me COLA, and since it was their mistake they were not going to ask for repayment. At issue is the method of calculating the COLA in the first place. The plan book outlines simply that after 3 years you get COLA added to your payment, and in particular that these increases “can be significant over time”. With their recalculation I went from “a significant” $460 per month COLA line item, to $160, hardly significant for 10 years of accrual. There is no methodology written in the plan book at all, just the declaration that you get it and the %. I would like to talk to someone about how many other claimants COLA have been reduced and any class action in regard to this