pvftovoc: 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/pvftovoc - from package: mgetty-voice

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

On Debian possible default full paths are:

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

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

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