Identifier not found - Noob C++ question

#include "stdafx.h"
#include <iostream>

using namespace std;

int _tmain()
{
	char input = '0';
	while(input != 'd' && input != 'g')
	{
		cout << "Please select a company to recieve a quote from\nDHL - (d)\nGlobalMail - (g)\n\n(select either g or d)->";
		cin >> input;
	}

	cout << "\n\n";
	
	switch (input)
	{
	case 'd':
		
         break;

	case 'g':
		cout << "GlobalMail, great choice! Please enter the weight of your parcel\n->";
		int weight = NULL;
		cin >> weight;
		weight = calcPostage(weight); //this line breaks
		cout << "Your package will cost R" << weight;
		break;
	}

	return 0;
}

int calcPostage(int weight)
{
	return weight * 108;
}

int calcPostage(int length, int width, int height)
{
	return (length * width * height) / 5000;
}</iostream>