Mysterious Error in Hotel Management Program - C

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C

I have made a program for hotel management. It has a problem that: In the Accounts function, it should reset all the flags of the registered members through the program. But there is a error that it does NOT. I have spent a lot of months, trying to debug this problem, but i couldn't. So please help me. Here is the code of the account function,

void accounts()
{
    int ttt=0;
    struct person payment;
    char aname[21], oname[21];
    char *namea;
    int chec=1, ver=0;
    long int recsize;
    recsize=sizeof(payment);
    f=fopen("C:\\HOTEL.DAT", "rb+");
    if(f == NULL){
        clrscr();
        cprintf("File could not be opened!");
        sleep(4);
        exit(0);
    }
    clrscr();
    cprintf("\n                   *** Pearl Guest House - Payments ***\n\n");
    cprintf("\r\r\rEnter the Name :");
    fflush(stdin);
    scanf("%[^\n]s", &aname);
    namea=strupr(aname);
    strcpy(oname, namea);
    while(fread(&payment, recsize, 1, f) == 1){

        if((payment.flag == 1) && (strcmp(payment.name,oname) == 0)){
            payment.pay=1;
            printf("\n\n Payment Received");
            fflush(stdin);
            getch();
            ver=1;

            fseek(f, -recsize, SEEK_CUR);
            fwrite(&payment, sizeof(payment), 1, f);
            break;

        }

    }

    if(ver!=1){
        printf("\n\n Record not Found!!!");
        fflush(stdin);
        getch();
    }
    //rewind(f);
    fclose(f);
    f=fopen("C:\\HOTEL.DAT", "rb+");
    if(f == NULL){
        clrscr();
        cprintf("File could not be opened!");
        sleep(4);
        exit(0);
    }

    while(fread(&payment, recsize, 1, f) == 1){
        if(payment.pay==0){
            chec=0;
            break;
        }
    }
    //rewind(f);
    f=fopen("C:\\HOTEL.DAT", "rb+");
    if(f == NULL){
        clrscr();
        cprintf("File could not be opened!");
        sleep(4);
        exit(0);
    }

    if(chec==1){
            while(fread(&payment, recsize, 1, f) == 1){
                payment.pay=0;
                fseek(f, -recsize, SEEK_CUR);
                fwrite(&payment, recsize, 1, f);
                ttt++;
                printf("%d", ttt);
            }

            printf("\n\n All payments recieved...\n\nSo, the payments flags are set to 0");
            fflush(stdin);
            getch();
    }
    printf("Before Fclose");
    fclose(f);
    printf("After Fclose");
}

This is my structure person:

struct s_office{
    char name[16];
    char phone[12];
    };
struct permanent{
    char addr[100];
    char phone[12];
    };

struct emergency{
    char name[21];
    char relation[11];
    char phone[12];
};

struct person{
    char name[21];
    char phone[12];
    char place[21];
    int roomno;
    int flag;
    char food;
    struct s_office office;
    char father[21];
    char fphone[12];
    struct permanent per;
    struct emergency emer1;
    char email[40];
    int finger;
    char dob[8];
    int cidate;
    int cimonth;
    int ciyear;
    int codate;
    int comonth;
    int coyear;
    int rent;
    int pay;
};

Here is a list of headers i included:

#include<conio.h>
#include<stdio.h>
#include<stdlib.h>
#include<ctype.h>
#include<string.h>
#include<dos.h>

I used Turbo C++ to write this code. When this is run, it runs successfully but the output is not what is supposed to be. (It is supposed to open the file(where is store data - HOTEL.DAT), read all the written functions one by one and then if it sees that all of them have pay variable = 1; it should say "All payments received..." and then it should set all of them to 0) I tried to debug and found out that most probably, the error is here:

while(fread(&payment, recsize, 1, f) == 1){
                payment.pay=0;
                fseek(f, -recsize, SEEK_CUR);
                fwrite(&payment, recsize, 1, f);
                ttt++;
                printf("%d", ttt);
            }

Here I suppose that the loop is ok because if i comment the contents of the loop, it runs n times. (if n = number of entries) BUT if i uncomment the contents it does not! This is the problem. Therefore it doesn't set all of them to 0. What i want is a solution to this problem and code so that it gives desired output(of setting every pay variable to 0)

Remember: This is a 14 year old kid trying to code; please help and answer politely and in detail;;; THANKS