gsmpb: 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/gsmpb - from package: gsm-utils

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

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