custom class operator overriding

Trying to override () operator in my Custom class Queue in order to be able to copy a few element from one Queue to another, smth like that:

Queue q1(2);
Queue q2(4);
q1.enqueue(1);
q1.enqueue(2);

q2.enqueue(3);
q2.enqueue(4);
q2.enqueue(5);
q2.enqueue(6);

q2(0, 2) = q1;
cout << "q1: " << q1 << endl;
cout << "q2: " << q2 << endl;

So, expected result is when q2 is {1,2,5,6} and q1 {1,2}. I've written some code to get such result:

    Queue &Queue::operator=(Queue &q)
    {
         Queue buffer(this->size, this->timeToServe);
        for (int i = 0; i < end; i++)
        {
            buffer[i] = this->queuePtr[i];
        } 
        delete[] queuePtr;
        this->end = q.size;
        queuePtr = new int[end]; 
        for (int i = 0; i < end; i++)
        {
            queuePtr[i] = q.queuePtr[i];
        }
         for (int i = 0; i <= 2; i++) {
            queuePtr[i] = buffer.queuePtr[i];
        } 
        return *this;
    }
//inside Queue class
    Queue operator()(int b, int e) {
            this->cBegin = b;
            this->cEnd = e;
            return *this;
        }

But my Queue &Queue::operator=(Queue &q) is never executed in such usage (it works perfectly with q2 = q1). Why? Thanks in advance!