gsmsmsspool: 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
/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/gsmsmsspool - from package: gsm-utils

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