Hello Reynaldo,

a device for SMB can be

877: ADSL over analog telephone lines (ADSL2/ADSL2+ Annex A and Annex M)

there are modules for ISR 1800,2800,3800 but these routers are more expensive and addresses the needs of a branch office.

about configuration:

actually there are different ways and depends from provider:

PPP over ATM

PPP over Ethernet over ATM

I would suggest to ask to your provider what kind of service they offer.

example for pppoe over ATM see

http://www.cisco.com/en/US/tech/tk175/tk15/technologies_configuration_example09186a008071a6c3.shtml

Hope to help

Giuseppe