sipwitch-config: 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/sipwitch-config - from package: libsipwitch-dev

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

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