Cisco WAN :: 857 - How To Route Traffic Over Remote Location Internet

I have a customer which has a main location office and a remote one. Recently we interconnect their facilities using a local ISP service called Virtual Connectivity, which basically is a private network which can be accessed over aDSL or any other data circuit. They are using Cisco 888 routers to interconnect both sites.At the main site the customer also has an Internet circuit (with a Cisco 857 router)and he wants to remove the Internet circtuit from the remote site and provide them access over their main location Internet circuit.At the primary offices, we installed Cisco 2811 router as a gateway to route the Internet and remote network traffic over the required data circuit. Everything is working fine, but we can not access Internet from the remote location over the circuit installed a the main site. I understand this is a routing issue, since the traffic hits the main office network it does not knows how to reach the Internet. I am assuming this routing must be set into the main office Cisco 888 router (installed by the ISP to interconnect to their private cloud) in order to properly route it over the Internet circuit.Since I already have access over the Internet router and the gateway router at the main site, but not into the ISP router, is there any other way I can make this configurtion over the routers I already have access?