T22P 2 account VPN and not

[s.pisani]

Hello, I'm trying to use a T22P with 2 account.
Firmware Version 7.73.0.40
Hardware Version 5.0.0.60

I have a VPN active with and external PBX and the account1 is OK.
I tried to create a second account with a second PBX in the local net.
The registration is OK, the call too but there is no audio.
The problem is that the phone uses the IP from VPN (tuno) as own audio IP in INVITE.
There is a way to force phone to use outgoing nterface IP instead?

Code:

esw0      Link encap:Ethernet  HWaddr 00:15:65:2E:86:B2  
          inet addr:192.168.4.28  Bcast:192.168.4.255  Mask:255.255.255.0
          inet6 addr: fe80::215:65ff:fe2e:86b2/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
          inet addr:192.168.203.22  P-t-P:192.168.203.21  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1