Yeah, looks like this whole thing is a major clusterf***! Something was fishy about this person's story from the start. I sincerely hope that Canaan Online Shop really has a professional staff capable of handling things like this, and that they will be able to resolve this case. It's important that customer support remain professional and look at every case from all possible angles, regardless of pressures that some clients try to impose on them. In this case, I suspect that the OP is a scammer who didn't get his way and decided to try to extort money by creating this false accusation.

@Canaan Online Shop, I'm glad to see that you're taking a stand and refusing to cave in. I have been in these situations myself and know how important it is to remain calm, professional, and to not be intimidated by threats. If you are in contact with a real customer, try to get a signed message from the original address. That would be definitive proof that the scammer is lying and that it is safe to return the funds to that address.