When you delete a channel we soft delete it and make all messages up to that point invisible. This way if you were creating the same channel again (same ID) you would not see the previous messages. There is some information attached to the channel that we hard delete to make sure it cannot resurface, that's the channel custom data, the member list and the id of the creator. In order to fully recover full channel data and messages, you need to re-create the channels you listed using the APIs and provide that information. Once that's done we can perform a manual operation that will bring back the deleted messages.