Expected invocation on the mock at least once, but was never performed

First of all, I googled all SO posts on this but none helped me. I get the exception on the subject on below piece.

 [Test]
    public void TestInv()
    {
        string inReference = "123";
        _Service.Setup(q=> q.InvoiceS(inReference ));
        _Service.Verify(q => q.InvoiceS(inReference ), Times.AtLeastOnce());
    }