pon: 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 Debian possible default full paths are:

/usr/bin/pon - from package: ppp

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

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