Help with 2D arrays

[bool maybe]

So I'm trying to write a program that displays available seats on an airplane (7 rows with 4 seats each). The user is supposed to specify a row and column of a seat with a number(1-7) followed by a letter(A-D) like so:

7a
6c
6d

The above are just some possible examples. After each seat is selected a display of the available seats should display with an "x" appearing wherever a seat is occupied. line 154 is meant to accomplish this task but it doesn't appear to be working. Any advice?

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>

const short COLUMNS = 4;
const short ROWS = 7;

//initializes seats array
void initialize(char seats[][COLUMNS]);

//converts digits (0-3) to chars (A-D)
//returns letter A-D corresponding to digit
char convert(short digit);

//converts char (A-D) to a digit (0-3)
//returns digit 0-3 corresponding to column_char
short convert(char column_char);

//display seats array
void display(char seats[][COLUMNS]);

//initializes vacancy array so each element is true
void initialize(bool vacant[][COLUMNS]);

//places an "x" for a specified place
//row and column specify coordinates of place
//asks user to input row/column if the position is already occupied
void register_place(bool vacant[][COLUMNS], char seats[][COLUMNS], short row, char column_char);

int main()
{
	using namespace std;

	char control = 'y';//this variable is used by user to stay in or exit out of do-while loop

	do
	{
		char seats[ROWS][COLUMNS];
		bool vacant[ROWS][COLUMNS];
		initialize(seats);
		initialize(vacant);
		display(seats);
		short row;
		char column_char;

		//TESTING
		while(true)
		{
			cout << "Enter row/column: ";
			cin >> row >> column_char;
			register_place(vacant, seats, row, column_char);
		}

		cout << "\n\nWould you like to run the program again? (Y/N): ";
		cin >> control;
		while ((control != 'y') && (control != 'n'))
		{
			cout << "Incorrect input. Would you like to run the program again? (Y/N): ";
			cin >> control;
			control = tolower(control);
		}
		
	}while(control == 'y');
	
	cout << "Press key to exit: ";
	char exit;
	cin >> exit;

	return 0;
}

void initialize(char seats[][COLUMNS])
{
	using namespace std;
	for(short i = 0; i < ROWS; i++)
	{
		short count(0);
		for(short j = 0; j < COLUMNS; j++)
		{
			seats[i][j] = convert(count);
			count++;
		}
	}
	return;
}

void initialize(bool vacant[][COLUMNS])
{
	using namespace std;
	for(short i = 0; i < ROWS; i++)
	{
		for(short j = 0; j < COLUMNS; j++)
		{
			vacant[i][j] = true;
		}
	}
	return;
}

char convert(short digit)
{
	using namespace std;
	switch (digit)
	{
		case 0:
		return 'A';
		
		case 1:
		return 'B';
	
		case 2:
		return 'C';
	
		default:
		return 'D';
	}
}

void display(char seats[][COLUMNS])
{
	using namespace std;
	for(short i = 0; i < ROWS; i++)
	{
		cout << i+1 << "  ";
		for(short j = 0; j < COLUMNS; j++)
		{

			cout << seats[i][j];
			if(j == 1)
			{
				cout << "  ";
			}
		}
		cout << endl;
	}
	return;
}

void register_place(bool vacant[][COLUMNS], char seats[][COLUMNS], short row, char column_char)
{
	using namespace std;
	column_char = toupper(column_char);
	short column = convert(column_char);
	while(!vacant[row][column])
	{
		display(seats);
		cout << "Invalid position. Enter new coordinates: ";
		cin >> row >> column_char;
		column_char = toupper(column_char);
		column = convert(column_char);
	}
	vacant[row][column] = false;
	seats[row][column] = 'x';
	return;
}

short convert(char column_char)
{
	using namespace std;
	if(column_char == 'A')
	{
		return 0;
	}
	else if(column_char == 'B')
	{
		return 1;
	}
	else if(column_char == 'C')
	{
		return 2;
	}
	else//column_char == 'D'
	{
		return 3;
	}
}

[bool maybe]

Never mind. I figured it out.