Hello!
I would like to help you with this task. I suggest you to use OpenVPN tunnel, it will solve your problem. OpenVPN is strong, flexible and good VPN protocol. It supports Windows, Linux, MacOS, iPhone, Android devices. I use SIP over OpenVPN and it works great.
About my experience: I have big experience with network administration (iptables, tcpdump, iproute2, snat, dnat,...), big experience with OpenVPN servers. Experience with variety of different OpenVPN configurations, such as serial connection of 3 servers, for maximum security. OpenVPN over IPv6.
My other skills and reviews you can see in my profile.
Hope for cooperation!
Thank you!