The following review written by one of the Software Informer contributors applies to version 2.4
Dekart SIM Manager 2.4 is a SIM card reader for Windows. If you have a SIM card reader, a device that can read SIM cards and connects to your computer, you can use this application to access the contents of the SIM cards.
Dekart SIM Manager can read from and write to SIM cards. The main use you would give this application is to organize the contents of the card. You can download all your contact information and edit it on your computer. You can also save your contacts to the computer or send them back to your phone. This comes in handy when your phone is not adequate for data entry (i.e. its keyboard sucks). Dekart SIM Manager also has a feature which allows you to copy a SIM card entirely. So, in case you lose it, you can replace the card and send the information right back on it. It can also help in unlocking SIM cards. Usually, SIM card reading applications are not easy to use. However, Dekart's take works really good. All your contact details are easy to find and they can be edited by simply double clicking on the contact's name.