wvdial: 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/bin/wvdial - from package: wvdial

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

On Debian possible default full paths are:

/usr/bin/wvdial - from package: wvdial

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

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