Call pickup group doesn't work

Hi, I have some problems with the CALL PICKUP GROUP. I want to describe what’s the situation: I have 3 extension, called 150, 597, 598. I’ve inserted these into the same call pickup group by inserting the following lines into the extension configuration (using the freepbx interface):

callgroup=1
pickupgroup=1

After that, I’ve controlled into the FEATURE CODES section if the code for the pickup group is avalaible: everything is ok!
I’ve checked also the configuration files called sip_additional.conf and features.conf, where there’re the extensions and pickup call group configuration.

So, I think that everything is all right and I try to pickup a call. From 150 I call 597 and fron 598 I try to pickup the call by digiting *8. After that, 597 stop to ring and the call is transfered to 598, but:

1)150 doesn’t stop the ringing;
2)from 598 the users can’t listen anything.

What happens? I don’t understand what I’m wrong.
Please, if you want, help me!
Thanks so much.

See you later.

Roberto