Strange behaviour (difficult to hangup)

There’s a strange behaviour built-in in Freebpx (I guess), I don’t know if someone of you could help disable it:

say that I place a call, and my counterpart answers. I change my mind and I want to hang up te phone. The strange beaviour is the fact that the PBX call me back and restart the communication againg! This is very annoying.

Is there a way to disable this behaviour?

Thanks
Rgds
Stefano

And what type of service is this (zaptel card)
Sounds like the phone think you put them on hold