Using Just *one Simcard* In Your Phone To Access,receive And Connect As Many Lin

    SEE HOW IT WORKS
   
1) Insert the simcard of the network you wish to keep at home in your handset and switch on your phone.
2) press the following bottons on your phone. **62* (then enter the phone number you want to permantly retain in your phone) then # ok/yes/send.
3) your phone will display active for:Asynchronous data,services inactive for all services or completed
4) remove the simcard you wish to keep at home from the phone.
5) Insert the simcard you want to travel along with in the phone and switch on your phone.
6) call any of the line it will automatically ring in the same phone.


                                  HOW TO CANCEL IT
  1) Put the line you kept at home in the phone and switch on the phone.
2) Press ##67# or ##62# or ##21# then send.
                                     

I agree. These are just regular GSM codes which most carriers should have in their user guide/manual. See link below.  Forwarding is not free though. Most carriers will charge for it. So, you better check with your carrier to find out exactly how much they charge.

http://www.mobileshop.org/usertech/gsmcodes.htm

It's just voice calls that are forwarded.  SMS and MMS are not. I am assuming that's what you mean by message.