There are a number of forwarding and callback services that people have used here over the last few years. If you do a search you can find lots of different people with experience with different companies. I have been using Telcan.net for a number of years and have been happy with them. They provide options for both call forwarding and callback. In the last two months I have tried Skype for forwarding. I just got back from Beijing and used Skype to forward two US cell phone numbers to my China Mobile prepaid SIM and it worked flawlessly from what I could tell. Quality was outstanding.