Question: Is there a way to explicitly close a GPRS connection?  

I'm setting up a connection with `ConnectionManager` and I've set the cache time to 10 seconds. Anyway after releasing it, the connection is still on, forever, alas I cannot use the registry key `gprs_by_if_device_off`. I'm using plain C++. 

My idea is to simulate the activity of the windows button "disconnect data connection", but I really cannot understand what it does under the curtain.

Answer: 
You need to terminate the remote access connection using RasHangUp with the handle you got from RasEnumConnections. 

PS know that this answer is a bit late, but hope it helps someone! ;)

RasHangUp <http://msdn.microsoft.com/en-us/library/ms897108.aspx> , RasEnumConnections <http://msdn.microsoft.com/en-us/library/ms897095.aspx>
Have you taken a look @ ConnMgrReleaseConnection ?

<http://msdn.microsoft.com/en-us/library/bb416503.aspx>