What's difference between them?

Question

What's difference between them? I don't know between 'in connection with' ' in regard to' and 'in reference to'.

1. I'm calling in connection with the order we placed.

2. I'm calling in regard to the order we placed.

3. I'm calling in reference to the order we placed.

Answer 1

There is no difference, really. The second one just goes with the sentence better.