How implement tariff class

Hi all,

I'm trying to implement a proprietary driver for connecting to Omnitel SMSC. 
THe main problem I've found is how to manage tariff classes. It seems not to 
be implemented yet in any smsc driver.

That is: how to say to a dirver what tariff class it has to use when delivery 
a sms to the smsc?

Could some one tell me if there is some valid example I may use for my task?

Thanks

Francesco Emmi 
A-Tono