How to best convert .wav to .3gpp
You can convert WAVE Audio Files directly to 3GPP Media Files (.wav to .3gpp conversion) quite easily. Such attempts typically relate to users searching for ways to encode WAV audio to 3GPP video.
Numerous (online) converters and audio editing programs, such as FormatFactory or SUPER, should allow you to import WAV audio files and export them in 3GPP format.