talkwith: 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/sbin/talkwith - from package: speakup-tools

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

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