First, here is the code:
Main.CPP
Code:
#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include "PBClass.h"

using namespace std;

PhoneBook::PhoneBook* PB = new PhoneBook::PhoneBook::PhoneBook();

int main(int argc, char *argv[])
{
    PB->AddPerson();
    system("PAUSE");
    return EXIT_SUCCESS;
}
PBClass.h
Code:
#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

using std::string;

namespace PhoneBook
{
    class PhoneBook
    {
        private:
            struct person
            {
                int number;
                string f_name;
                string l_name;
            };
            std::vector<person> PVec;
        public:
            PhoneBook();
            ~PhoneBook();
            void AddPerson(person *pb);
            void AddPerson();
            //void RemovePerson(person *pb);
    };
}
PBFunctions.CPP
Code:
#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include "PBClass.h"

using namespace std;

namespace PhoneBook
{
    void PhoneBook::AddPerson(PhoneBook::person *pb)
    {
        PVec.push_back(*pb);
    }

    void PhoneBook::AddPerson()
    {
        person *npb;
        cout<<"Please put in the phone number of the person:\n";
        cin>>npb->number;
        cout<<"\nPlease input the first name of the person:\n";
        cin>>npb->f_name;
        cout<<"\nPlease input the last name of the person:\n";
        cin>>npb->l_name;
        cout<<endl;
        PVec.push_back(*npb);
        //cout<<PVec.end();
    }
}
Now here is the problem: it won't compile. Everytime I try I get this error:

[Linker error] undefined reference to `PhoneBook::PhoneBook::PhoneBook()'
and to be perfectly honest, I'm lost as to what to do.
As always, any help would be appreciated.