If I was you, I would report this person - all allegations of cheating are taken seriously as schools could face serious consequences id they don't. Anyway, someone in my year reported a person using their phone to look up the mark scheme during my CIE English Language exam last month (the invigilators were too stupid to notice); that person has since been disqualified from their English GCSE.
If not for yourself, report this person for the benefit of others - don't let them increase the grade boundaries!