Can you call a cell phone in the microwave?

hello, the grid is frequency selective. The hols work like radiating apertures. higher the frequency is greater is the leackage as you mentioned. I believe the shielding attenuation is around 35 to 40 dB at 2.4 GHz and this explains why you can still hear the microwaveoven even 20 m away on a special radio tuned to 2.4 GHz, or on a spectrum analyser.