sflphone: 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/sflphone - from package: sflphone-gnome

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

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