SMS from PC using Dongle/GPRS Modem / ??

Hi All, simple Q, I've trolled and trolled and cannot seem to find what I really need to know on this.

I need to build an app (in whatever language) to send and receive SMS's from a PC using a Sim Card Dongle / GPRS Modem (i.e. not a http gateway service).

All I can seem to find is that I need to use AT commands ? Surely Nokia / some other provider gives an API for doing something like this ?

Do I really need AT commands ?

Any help on what modem/gprs etc I need and what API's / options I have would be greatly appreciated.

Thanks

Chub.