try this out; i am not sure if something is left out
isdn switch-type primary-net5
controller E1 1/0
framing NO-CRC4
pri-group timeslots 1-31
description Link To Telco
interface FastEthernet0/0
description Link to Internet
ip address a.b.c.d c.d.e.f
h323-gateway voip interface
h323-gateway voip bind addr a.b.c.d
interface Serial1/0:15
isdn switch-type primary-net5
ip route 0.0.0.0 0.0.0.0 w.x.y.z
voice-port 1/0:D
compand-type a-law
dial-peer voice 1 pots
destination-pattern 00025641T
port 1/0:D
dial-peer voice 7 voip
session target ipv4:p.q.r.s
codec g729br8