I am interested in purchasing a CHARLES-HUBERT watch model: 3857 - do you this model available?

We do not carry the model 3857.

What would happen if it be near cellphones?Will it become more inaccurate?

This is a mechanical watch, any source of magnetic field is bad for a mechanical movement. The reason being, these are regulated by a balance wheel driven by a coiled spring, both are metal, if these become magnetized they can become highly inaccurate. Cell phones utilize powerful magnets for multiple reasons, primarily vibrate function and speakers. This is the bain of any mechanical movement, super high end mechanical watches are even subject to this weakness and high end watch makers put a lot of work into making them less susceptible to magnetic fields (Rolex Milgauss/Omega Railmaster), but they still too are subject to magnetic interference. If you need something reasonably impervious to being near a source of magnetism, look for a quartz movement.