Hello,
For the dialog module to actually send a spoofed BYE to both endpoints when the timeout is reached, an attribute must be set that says to do that, because the default behaviour is to time the dialog out only, not to end it.
If you want to set it globally:
http://kamailio.org/docs/modules/4.3.x/modules/dialog.html#idp1892976
If you want to set it on a per-dialog basis:
http://www.kamailio.org/wiki/cookbooks/4.3.x/pseudovariables#dlg_ctx_attr
-- Alex