VPN Client Enable ATA?

Hi All,

I have to setup a centralized Asterisk server and have to configure 20+ extensions for 20+ location nationwide for intercom calling. B/w In my country sip port is block so all we need is to setup a centralized VPN server (Open server) on same machine where asterisk will be installed.

So my question is there any ATA that has a VPN client or OpenVPN built in? That way I could connect securely to my Asterisk Server from all 20+ remote locations.

Waiting for your kind and quick response. thanks in advance.