As the messaging function is taking place between the XPLORA App and the watch, it is not possible that two watches can chat with each other. However, the watches may call each other, provided that they are in the contact list.
Every person who wants to exchange messages with the watch, would need to download the XPLORA 3 & 3S or XPLORA GO App on his Smartphone, and be in the contact list. It does not require administrative rights in order to write and receive messages from the watch.
A quick user guide on how to add contacts can be found here.