chat: 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 CentOS possible default full paths are:

/usr/sbin/chat - from package: ppp

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/chat - from package: ppp

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

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