Yes. You can disable it by editing the file agent_console.tpl
Go to this directory
/var/www/html/modules/agent_console/themes/default
Make a backup of the agent file using this command
cp agent_console.tpl agent_console.tpl.backup
Open the file agent_console.tpl for editing (vi or nano)
Search for this entry CLASS_BOTON_BREAK
You will see it among these 3 lines, the middle line contains the match
<button id="btn_hangup" class="issabel-callcenter-boton-activo">{$BTN_COLGAR_LLAMADA}</button>
<button id="btn_togglebreak" class="{$CLASS_BOTON_BREAK}" >{$BTN_BREAK}</button>
<button id="btn_transfer" class="issabel-callcenter-boton-activo" >{$BTN_TRANSFER}</button>
Delete the middle line. Your code should now look like this:
<button id="btn_hangup" class="issabel-callcenter-boton-activo">{$BTN_COLGAR_LLAMADA}</button>
<button id="btn_transfer" class="issabel-callcenter-boton-activo" >{$BTN_TRANSFER}</button>
Save your changes and test.
IF you do encounter problems (i have only tested this very minimally) you can issue this command to revert the file back from your backup you made.
cp agent_console.tpl.backup agent_console.tpl