c++ database.it should let you enter an account but doesnt save what i put in i think

[sethss]

#include<iostream>
#include<fstream>
#include<iomanip>
#include<cstdlib>
#include<cstring>
using namespace std;

const int NAME_SIZE = 25;
const int ADDR_SIZE = 30;
const int CSZ_SIZE = 30;
const int PHONE_SIZE = 15;
const int DLP_SIZE = 20;
int NUM_RECORDS = 0;



void write_account();
void display(int num);
void display_all();
void display_sp(int num);
void delete_account(int num);

struct Account{
    char name[NAME_SIZE];
    char addr[ADDR_SIZE];
    char csz[CSZ_SIZE];
    char phone[PHONE_SIZE];
    double balance;
    char dlp[DLP_SIZE];
};

int main()
{
	char ch;
	int num;

	do
	{
		cout<<"\n**********************MAIN MENU*********************************";
		cout<<"\n1. Enter a New Customer Account";
		cout<<"\n2. Display a Customer Account";
		cout<<"\n3. Delete a Customer Account";
		cout<<"\n4. Change a customer account";
		cout<<"\n5. Display All Customer Accounts";
		cout<<"\n6. EXIT THE PROGRAM";
		cout<<"\nEnter Your Option (1-6) ";
		cin>>ch;

		switch(ch)
		{
            case '1':
                write_account();
                break;

            case '2':  // display account number
                cout<<"\n\n\tEnter The account No. : ";
                cin>>num;
                display(num);
                break;

            case '3':
                cout<<"\n\n\tEnter The account No. : ";
                cin>>num;
                delete_account(num);
                break;

            case '4':
                cout<<"\n\n\tEnter The account No. : ";
                cin>>num;
                display_sp(num);
                break;

            case '5':
                display_all();
                break;

            case '6':
                cout<<"\n\n\tThank you come again";
                break;

            default :cout<<"\a";
		}
        cin.ignore();
		cin.get();
	}while(ch!='6');


	return 0;

}
    void write_account()
    {
        Account ac = {"","","","",0.0,""};
        double tempBalance;
        cout << "Name: ";
        cin.ignore();
        cin.getline(ac.name, NAME_SIZE);
        cout << "Address: ";
        cin.getline(ac.addr, ADDR_SIZE);
        cout << "City, State, ZIP ";
        cin.getline(ac.csz, CSZ_SIZE);
        cout << "PHONE # : ";
        cin.getline(ac.phone, PHONE_SIZE);
        cout << "Balance: ";
            cin >> tempBalance;
            if (tempBalance < 0 ){
                ac.balance = tempBalance;
            }
        cout << "Date of Last Payment: ";
        cin.getline(ac.dlp, DLP_SIZE);

        fstream customers("cust.dat", ios::app | ios::binary);
        customers.write(reinterpret_cast<char *> (&ac), sizeof(ac));
        customers.close();
        NUM_RECORDS++;
    }

    void display(int num){
        Account record;
        fstream inventory("cust.dat", ios::in | ios::binary);
        // Now read and display the records.
        inventory.seekg(num* sizeof(record), ios::beg);
        inventory.read(reinterpret_cast<char *>(&record), sizeof(record));

        cout<< "Name: " <<  record.name << endl;
        cout<< "Address: " <<  record.addr << endl;
        cout<< "City, State, Zip: " <<  record.csz << endl;
        cout<< "Phone Number: " <<  record.phone << endl;
        cout<< "Current Balance: $" <<  record.balance << endl;
        cout<< "Date of Last Payment " << record.dlp << endl;
        // Close the file.
        inventory.close();
    }

    void display_all(){
        cout<< "\n";
        cout << "Displaying all records."<<endl;;

        Account record;
        fstream inventory("cust.dat", ios::in | ios::binary);
        // Now read and display the records.
        inventory.read(reinterpret_cast<char *>(&record), sizeof(record));
        while(!inventory.eof()){
        cout<< "Name: " <<  record.name << endl;
        cout<< "Address: " <<  record.addr << endl;
        cout<< "City, State, Zip: " <<  record.csz << endl;
        cout<< "Phone Number: " <<  record.phone << endl;
        cout<< "Current Balance: $" <<  record.balance << endl;
        cout<< "Date of Last Payment " << record.dlp << endl;
        cout<< "\n";
        inventory.read(reinterpret_cast<char *>(&record), sizeof(record));
        }
        // Close the file.
        inventory.close();
    }

    void display_sp(int num){
        Account record;
        fstream inventory("cust.dat", ios::in | ios::out | ios::binary);
        // Now read and display the records.
        inventory.seekg(num* sizeof(record), ios::beg);
        inventory.read(reinterpret_cast<char *>(&record), sizeof(record));

        double tempBalance;
        cout << "Name: ";
        cin.ignore();
        cin.getline(record.name, NAME_SIZE);
        cout << "Address: ";
        cin.getline(record.addr, ADDR_SIZE);
        cout << "City, State, ZIP ";
        cin.getline(record.csz, CSZ_SIZE);
        cout << "PHONE # : ";
        cin.getline(record.phone, PHONE_SIZE);
        cout << "Balance: ";
            cin >> tempBalance;
            if (tempBalance > 0 ){
                record.balance = tempBalance;
            }
        cout << "Date of Last Payment: ";
        cin.getline(record.dlp, DLP_SIZE);


        inventory.seekp(num * sizeof(record), ios::beg);
        inventory.write(reinterpret_cast<char *>(&record), sizeof(record));

        // Close the file.
        inventory.close();
    }

    void delete_account(int num){
        Account record;
        fstream inventory;
        fstream tempFile;
        inventory.open("cust.dat", ios::in | ios::out | ios::binary);

        if (inventory.fail())
        {
            cout << "\nError opening file.\n";
            inventory.close();
            exit(0);
        }

        // Now read and display the records.
        strcpy(record.name, "\0");
        inventory.seekp(num, ios::beg);
        inventory.write(reinterpret_cast<char *>(&record),sizeof(record));
        inventory.close();

        inventory.open("cust.dat", ios::in | ios::binary);
        tempFile.open("temp.dat", ios::out | ios::binary);
        inventory.read(reinterpret_cast<char *>(&record),sizeof(record));

        while (inventory)
        {
            tempFile.write(reinterpret_cast<char *>(&record),sizeof(record));
            inventory.read(reinterpret_cast<char *>(&record),sizeof(record));
        }
        inventory.close();
        tempFile.close();
        tempFile.open("temp.dat", ios::in | ios::binary);
        inventory.open("cust.dat", ios::out | ios::binary);
        tempFile.read(reinterpret_cast<char *>(&record),sizeof(record));
        while (!tempFile.eof())
        {
            if(record.name[0] != '\0')
            {
                inventory.write(reinterpret_cast<char *>(&record),sizeof(record));
            }
            tempFile.read(reinterpret_cast<char *>(&record),sizeof(record));
        }
        tempFile.close();
        inventory.close();
        cout << "\nDeletion successful.\n";
    }