As far as i know, afternic is not a registrar, so there is nothing to "transfer".
I only know of listing domains for sale there or parking them. If you want to stop the listing, delete the names from the "my account list". This would stop them for being for sale or parked, but have no effect on the registration. Afternic does not require exclusive listings, so you can leave them listed for sale there and list them at sedo or other sites at the same time if the other site doesn't require exclusive listings.
If you are referring to transferring the parking, you do that my changing the DNS servers at your registrar.