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

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

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