Samsung NX-308 - Manual (Page 39)

9-3 HOW TO REMOVE THE HANDSET CORD FROM THE HANDSET
NX-SERIES HYBRID KEY SYSTEM INSTALLATION SECTION
2 - 34
Driver
Line holder
Insert the sharp-edged one
(ex:driver, pincette,...) into the
slight gap of handset.
Slightly push the driver, and lift
up the line holder from handset.
Now, you have removed the line holder, and can see the modular
jack of the handset cord.