[avacado]

"You cannot remove “noise” from “content” in a recorded file. There is no way to separate them."

Nonsense! I do digital data processing of seismic data for a living. We remove noise all the time with band-pass filters. The cell phone noize would have a certain frequency range and can be easily removed.

[Tex-Con-Man]

In a recording, if you use band pass filters, you will remove everything within that frequency range. That may include noise AND content. If the noise is within the vocal range, the only way to reduce it's effect is flipping the phase on the noise and playing it with the original. But this has limited success as well. Unless the noise exactly matches the noise underlying the content, it can only reduce it.

The point is, once the noise and content are one file, separating them is not an exact science.