Welcome to the forums,I think I can help you out here...

When your phone is on STANDBY,press the following buttons on your phone...

First press "#" then press "*" then press "MENU" then press the "Right" key. This should take you to a menu called "Trace Mode".

In this menu,your should see another menu called,"phone info" or something similar to that. Click on that,then you will see another that says "Phone Model". Finally click on there and it should say your phone model followed by the letter your looking for.

I am trying to update my i730s software but cant figure out how to find out what model i have- i730-A or i730-B- idens website tells you how to check on the i90s but not the i730s. or should i say it doesnt work on my phone. please help!