unicode2sms: 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/unicode2sms - from package: smstools

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

Error in other languages:
unicode2sms: bevel nie gevind nie
unicode2sms: comandă negăsită
unicode2sms: comando não encontrado
unicode2sms: commande introuvable
unicode2sms: command not found
unicode2sms: käsku ei ole
unicode2sms: không tìm thấy lệnh
unicode2sms: komanda nerasta
unicode2sms: Kommando nicht gefunden.
unicode2sms: kommandot finns inte
unicode2sms: komut yok
unicode2sms: nie znaleziono polecenia
unicode2sms: níor aimsíodh an t-ordú
unicode2sms: no se encontró la orden
unicode2sms: no s'ha trobat l'ordre
unicode2sms: opdracht niet gevonden
unicode2sms: parancs nem található
unicode2sms: perintah tidak ditemukan
unicode2sms: príkaz nenájdený
unicode2sms: příkaz nenalezen
unicode2sms: команда не найдена
unicode2sms: командата не е открита
unicode2sms: 命令找不到
unicode2sms: コマンドが見つかりません