Find the dead zone, prove it

You cannot make a call in the office you rent, and the landlord says the signal is fine everywhere. Start a measurement, walk the office, and mark a point with a photo by the windows and in the back rooms. Ten minutes. What comes out: a file with a timestamp, a position, signal strength, the serving cell and photographs of the rooms. Attach it and “the signal is fine everywhere” becomes a claim that can be checked — or refuted.