I had no idea what a PPP caller was, so I googled it....
http://www.raspppoe.com/
It says that the the program should be used for "method for establishing PPP connections through Ethernet adapters ". If the Neotel device is using USB, does that make a difference?
That won't work.
What you guys basically need is an old 56K Dialup Trick. A normal background pinging application to keep the connection alive.
http://www.download.com/BySoft-StayAlive-Pro/3000-2155_4-10794087.html
Get that program, latest Version.
If you are running Linux, look for an alternative. Default options of the program should keep the connection active, otherwise tweak as desired.
Just googled my behind off for you guys