Programs enabling conversion of the file:
If your objective is to convert the file from H264 to the file 3G2, you can use any of the applications listed. H264 to 3G2 conversion process in every program intended for this purpose (so-called converters) is very intuitive and everyone is able to manage converting a file.
However, bear in mind that the list may also include programs to support and work with the indicated extensions H264 and 3G2 - and not only converters. In such a case, you need to open the source file H264 and from the options available in the program, choose ”Save as... 3G2" or "Export to 3G2".