from the conversation posted on the original page, it looked fairly clear that you were avoiding giving the registered post #. The registered post # also seems to have not been used as per comments on the following pages. Might be a better idea to actually address the issue instead of insulting the user and threatening them.
They "threatened" you as a response to your threat of not giving them anything, not to say they were right in threatening you but, that was the course of event.
Being rude and abrupt with people is not going to get you anywhere other than make people think twice before making purchases from you in the future. If you clearly advised the process you were taking and responded to request for the registered post tracking number initally, you could have stopped all this from occurring. Just something to think about for future encounters with buyers.