refcounter: command not found

Have You tried accessing the binary with the full path?

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/refcounter - from package: asterisk

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