I've been searching the Internet for ages looking for samples on sending USSD commands using .NET Compact Framework and C#. Someone did mention that it is achievable by using Microsoft.WindowsMobile.Telephony.Phone.

Does anybody have any ideas? Thanks

You need to use lineSendUSSD and lineGetUSSD. 

Thanks Neil. After going through the links that you provide, it seems like these extended TAPI functions are in C++.Does that mean that I have to write my own wrapper to implement both lineSendUSSD and lineGetUSSD in C#?

Thanks.

you can invoke the functions in c# just casting the types to equivalent types in c#