Can you call a cell phone in the microwave?

A microwave oven is not a Faraday cage because the door seal is non-conductive. Microwaves would leak out through the door seal except that in the door frame there is a profiled strip of aluminium called a quarter wave choke, which absorbs radio waves of a specific wavelength and is designed to absorb the wavelength used by the oven. This means that if the phone in the oven is using the same wavelength it will be blocked (or at least it should be), but if it using a significantly different wavelength it will get through.