I have a white flaky substance on my coping (see below). What is this and how do I remove it?
Calcium. Your pool is out of balance.
So what do I do to get it off? I assume this is my pool service company's issue as I pay them to handle this stuff.
It is your pool and your issue. That you pay for a service to handle it doesn't change anything. How do you measure the job they are doing?
If you get a proper test kit, you will know what is off chemically and can act accordingly. Strips that have pH, alk, chlorine, etc... are not accurate or reliable. Many, if not most services are weak in proper testing and dosing.
If I were caring for this pool going forward, I would verify the water's chems first and correct as needed. Pool chemistry is not that difficult, time consuming, or complex.
I would also take a flake of the substance on the coping and drop it in some water. If it dissolves, it would likely be salt, If it didn't do anything, I would add some muriatic acid to see if it dissolves, making it likely to be what is known as scale, a calcium based deposit. Those are the two main types of deposits.
This doesn't appear to be effervescence, the leaching of calcium from the concrete surface.
Is this a uniform deposit around the pool or just at the well trafficked areas? You can try washing it with either diluted muriatic (3 water 1 acid) or white vinegar and a stiff brush.