tcp_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/tcp_call - from package: ax25-tools

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

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