pvftowav: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/pvftowav - from package: mgetty-voice

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/pvftowav - from package: mgetty-pvftools

You may install the required package with command apt-get install {package}

Error in other languages:
pvftowav: bevel nie gevind nie
pvftowav: comandă negăsită
pvftowav: comando não encontrado
pvftowav: commande introuvable
pvftowav: command not found
pvftowav: käsku ei ole
pvftowav: không tìm thấy lệnh
pvftowav: komanda nerasta
pvftowav: Kommando nicht gefunden.
pvftowav: kommandot finns inte
pvftowav: komut yok
pvftowav: nie znaleziono polecenia
pvftowav: níor aimsíodh an t-ordú
pvftowav: no se encontró la orden
pvftowav: no s'ha trobat l'ordre
pvftowav: opdracht niet gevonden
pvftowav: parancs nem található
pvftowav: perintah tidak ditemukan
pvftowav: príkaz nenájdený
pvftowav: příkaz nenalezen
pvftowav: команда не найдена
pvftowav: командата не е открита
pvftowav: 命令找不到
pvftowav: コマンドが見つかりません