Used stamps exchanges.

Have received a postcard from China with a club-ID (Cn-352). I cannot give feedback to this since there are no stamps involved. Probably some misunderstanding. Can I get the username and contact the sender and sort this out?

I have been in contact with him. Most likely misunderstanding. When it is sorted out, we will have another happy club-member?

Here the situation was the same:
http://100stamps.club/stamps/CN-353