The short answer to this is NO. Although most window films, including "ceramic films" or "IR films" contain some form of metal. There is no evidence to suggest they block any signal at all. To provide a better understanding as to how much metal is used in window film imagine this.... If you were to paint the roof of a six story building. The paint would equate to the metal and the building the film. As you can see, there is an extremely small amount of metal. Not enough to disrupt a cellular signal. Another example would be to think about all of the times your cell phone worked in rooms where there were no windows at all.
Point is, your windows are not the only source of signal.
This is a myth that originates from auto glass tinting. When auto tint was introduced with metal it was found to interfere with radio reception. But, only a few vechicles in which the antenna is in the rear window glass. Funny how information can get distorted over time.