Ciao Ale, grazie innanzi tutto per la risposta.
Purtroppo il fornitore VOIP mi ha risposto picche

:
"
la problematica da lei indicata è da individuarsi nella configurazione del
centralino o della rete, in quanto si tratta di un problema di NAT e o
firewall, per cui è estraneo al nostro servizio."
Per cui ora spero solo nell'aiuto degli amici .....
Di sotto le righe del test sul Firewall che a me non dicono nulla.
Grazie ancora In anticipo sul seguito se vorrai darmi altro aiuto
Mario
3CX Firewall Checker, v1.0. Copyright (C) 3CX Ltd. All rights reserved.
<19:29:45>: Phase 1, checking servers connection, please wait...
<19:29:45>: Stun Checker service is reachable. Phase 1 check passed.
<19:29:45>: Phase 2a, Check Port Forwarding to UDP SIP port, please wait...
<19:29:47>: UDP SIP Port is set to 5060. Response received WITH TRANSLATION 1040::5060. Phase 2a check passed with WARNINGS. Some functionality will be LIMITED. For more information, please visit
http://www.3cx.com/blog/docs/firewall-checker/<19:29:47>: Phase 2b. Check Port Forwarding to TCP SIP port, please wait...
<19:29:47>: TCP SIP Port is set to 5060. Response received WITH TRANSLATION 1040::5060. Phase 2b check passed with WARNINGS. Some functionality will be LIMITED. For more information, please visit
http://www.3cx.com/blog/docs/firewall-checker/<19:29:47>: Phase 3. Check Port Forwarding to TCP Tunnel port, please wait...
<19:29:48>: TCP TUNNEL Port is set to 5090. Response received correctly with no translation. Phase 3 check passed.
<19:29:48>: Phase 4. Check Port Forwarding to RTP external port range, please wait...
<19:30:05>: UDP RTP Port 9000. Response received correctly with no translation. Phase 4-01 check passed.
.... OMISSIS Righe da 9001 .... a 9048 tutte check passed.
<19:30:05>: UDP RTP Port 9049. Response received correctly with no translation. Phase 4-50 check passed.
Application exit code is 2