telegram: 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/telegram - from package: orville-write

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

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