overloaded less than (<) operator for sorting objects in several ways

If a class has overloaded an operator to facilitate sorting its objects by a particular attribute, is there a way to overload the operator again to sort by another attribute? For example, the class below has overloaded the less than < operator to compare its data member minutes, is there a way to do the same for its data member hours or would I just be better off creating a binary predicate for each sorting criteria? Thanks in advance.

class PhoneCall {
  friend ostream& operator<<( ostream&,const PhoneCall& );
  private:
      int minutes;
      int hours;

  public:
      PhoneCall(int = 0);
      bool operator<(const PhoneCall&);
};

ostream& operator<<(ostream& out, const PhoneCall& p) {
   out << "Phone call lasted " << p.minutes << " minutes" << endl;
   return out;
}

PhoneCall::PhoneCall(int ct) {
    minutes = ct;
}

bool PhoneCall::operator<(const PhoneCall& p) {
    bool less = (minutes < p.minutes)? true: false;
    return less;
}