I am the owner of c5x and have invoice of it. Still it was telling please contact to the owner
What was telling you to contact the owner, the device or the web site when you tried to get an unlock code? I don’t know how the device would do that, but if it is the device, do a factory reset on it. If it’s the web site when you try to get an unlock code, then you need to contact Mimosa Support. They’ll probably want a copy of your receipt.