gw-config: command not found

Have You tried accessing the binary with the full path?

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

[root@server ~]# echo $PATH

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/gw-config - from package: kannel-dev

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