Save as viaTalkSetCallForward or any other name as desired.
From command line:
viaTalkSetCallForward 19521234567 mySecretPassword 19529876543

#!/bin/bash
#
#$1 = Login name
#$2 = Password
#$3 = Forward number

if [ "$1" = "" ];
then
	echo -e "$0\n Usage: $0   \n"
	exit 1
fi

curl -b /tmp/$1.cookie -L "https://support.viatalk.com/billing/user.php?op=menu&tile=callforward" >/tmp/$1-forward.html 2>/dev/null

result=`cat /tmp/$1-forward.html|grep callforward|head -1`
if [ "$result" = "" ];
then
	curl -c /tmp/$1.cookie -d "op=login&submit=submit&username=$1&password=$2" -L https://support.viatalk.com/billing/index.php>/dev/null 2>&1
fi

if [ "$result" = "" ];
then
	echo -e "Login Error\n"
else
	curl -b /tmp/$1.cookie -L "https://support.viatalk.com/billing/user.php?op=menu&tile=callforward&number=$1&forward_number=$3" >/tmp/$1-forward.html 2>/dev/null
	result=`cat /tmp/$1-forward.html|grep -A 6 "name=\"number\" value=\"$1\""|grep "$3"`
	if [ "$result" = "" ];
	then
		echo -e "Failed to forward $1 to $3\n"
		exit 1
	fi
fi
exit 0