"Hey everybody I use Chipmixer " it's easy to say that why hiding behind a username and a keyboard.
If you are right go ahead show your KYC and tell the people like a centralized exchange you used a mixing service.
You seem to fundamentally misunderstand the whole point of a mixer or why someone would want to keep their privacy. And for the record, I've never completely KYC with any crypto service ever, and I have no intention of starting now.
Who would send their documents and selfie and many more things they asked to site like this one?
I wouldn't trust them to refund your money even if you did send the things the are asking, and the risk of your documents ending up on some darknet market or being used by someone else for some shady activity is extremely high.
I've never used BestChange, but I find it very questionable that they allow exchanges to simply close claims like this. OP has obviously not been refunded, but OpenChange have now closed his claim 24 times without resolving it. Looking back through their previous ratings, there seem to be a number of other issues which have been closed without being resolved. BestChange therefore show OpenChange as having an unblemished 100% positive feedback, which is obviously not the case. Such a system allows any exchange to keep a perfect record so long as they are more determined than their victims, who will eventually give up renewing their claims.