linphonecsh: 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/linphonecsh - from package: linphone-nogtk

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

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