RK Henry wrote:
snip

I once called my favorite CFII to make an appointment. When she
answered the phone, there was a lot of background noise but we could
still converse. She was talking to me on her cell phone while she was
instructing. Obviously, it can work.

I used to work with an instructor who would routinely conduct business
on his cell while instructing (yes, he had other issues). But like you
said, this was at low altitude in the practice area, very near multiple
towers. Reception was not a problem.