What are the chances of none of them being scammed over the years if Best Change have been twisting the rating system so people can be scammed and they just cash in a commission.
There have been more than one scam accusation against BestChange in the past. The most visible one is here:
https://bitcointalk.org/index.php?topic=5219339.0The situation described then is similar to what OP is describing now. Made a payment to an exchange, the exchange then froze that deposit and demanded KYC. The exchange in question (although now inactive) is still listed on BestChange with a 100% positive rating and multiple "cancelled" claims.
But regardless of whether this is the first or the one hundredth time this has happened, BestChange need to do better. Their landing page says they only use "reliable and trusted" exchanges, and the exchanges are all "100% legal". They give exchanges a green check tick to show they have undergone "additional checks". If this is true then BestChange should have, at a minimum, a name, address and company registration for OpenChange that they can forward to OP to let him take forward his claim.