ax25_call: 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/ax25_call - from package: ax25-tools

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

Error in other languages:
ax25_call: bevel nie gevind nie
ax25_call: comandă negăsită
ax25_call: comando não encontrado
ax25_call: commande introuvable
ax25_call: command not found
ax25_call: käsku ei ole
ax25_call: không tìm thấy lệnh
ax25_call: komanda nerasta
ax25_call: Kommando nicht gefunden.
ax25_call: kommandot finns inte
ax25_call: komut yok
ax25_call: nie znaleziono polecenia
ax25_call: níor aimsíodh an t-ordú
ax25_call: no se encontró la orden
ax25_call: no s'ha trobat l'ordre
ax25_call: opdracht niet gevonden
ax25_call: parancs nem található
ax25_call: perintah tidak ditemukan
ax25_call: príkaz nenájdený
ax25_call: příkaz nenalezen
ax25_call: команда не найдена
ax25_call: командата не е открита
ax25_call: 命令找不到
ax25_call: コマンドが見つかりません