You are looking for a VWIC-2MFT-T1-DI. Two T1 ports with Drop and Insert for cross connecting TDM channels.
Here is a sample config with channels 1-12 for data and 13-24 for voice:
controller T1 0/0 (To Network)
framing esf
linecode b8zs
channel-group 0 timeslots 1-12 speed 64
(creates int ser 0/0:0)
tdm-group 1 timeslots 13-24 type e&m
description T1 circuit from Provider
!
controller T1 0/1 (To PBX)
framing esf
clock source internal
linecode b8zs
tdm-group 2 timeslots 13-24 type e&m
connect tdm1 T1 0/0 1 T1 0/1 2 (connects the tdm groups for voice to the PBX)
interface serial 0/0:0
(Enter data configuration here)
The cable used between your router and PBX may need to be a T1 crossover.
Mark
http://www.cisco.com/en/US/products/hw/routers/ps274/products_tech_note09186a00800f9d37.shtml