No, it is not. A microwave wavelength is 12.24 cm, while a 900mhz cellphone wavelength is 33.4cm and a 1800mhz cellphone has a wavelength of 16.7cm (BTW, your wifi also has a wavelength of 12.24cm)
EDIT: There is of course a huge difference in power output (W).
You agree with him in a way and at the same time disagree? Is that even possible.
Basic calculus?