What do you call "they don't care".
They replied to you with something not adequat, or that's because they haven't replied yet.
Because that's different. If that's because you didn't get a reply, it can be normal and acceptable. Just wait a bit.
(waiting for your update on this matter.)
I call they don't care that : "Hello. We checked your letter of guarantee. Your letter generated by coinmixer instead our service [banned mixer] " and no reponse since that. I use [banned mixer] not coinmixer, i use the same link i use last time and i send the link to support but they don t care and doesn't respond.
I mix my coins on crytpomixer.io and you tell me it's not your problem. I 'm think it's your responsability to assure customers coin's security