dialtest: 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/dialtest - from package: hylafax+-client

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

On Debian possible default full paths are:

/usr/sbin/dialtest - from package: hylafax-server

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

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