Freeswitch Play a sound in ring group when brigde multi call

Question

Im using freeswitch to build our PBX. My case when have incomming call to a ring group with strategy is rollover, i want to play just one ringtone file when call bridge from user A->B->C in ring group. Currently if i set that"

session:setVariable("ringback", ring_group_ringback);       
session:setVariable("transfer_ringback", ring_group_ringback);

session:preAnswer();

The ring will reset after bridge new extension to call

I had tried to using uuid_displace but it not playsound

im using version freeswitch v1.10.8

Please help