Setting up new Agents using VPNs

Hi Everyone!
I am new to the community but not in the business. I am running a big firm which is providing software services to the clients all over the world. 
Sorry, I can’t disclose the company name. 
The issue is that my customer used to get engaged with the customer via the internet calling system. As we are focused on across the world people, we have to switch VPNs to the targeted country so that we bear the least cost of calling. (Sorry, if you don’t understand that)
Anyhow, the problem begins when there is a lot of burden and my employees are unable to switch the VPN to the calling country. Yes! they can do so, but when there is a lot of calls, we missed many in a day in rushy conditions.
i dont want to increase more individual cost to divide the customers actually. Tell me the way out so that the VPN switched to the relevant country automatically.

Thanks