stunc: 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/stunc - from package: sofia-sip-bin

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

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