Does a divorce occur if the wife speaks on her phone after an oath of divorce was sworn that she would not speak on it, and does the ruling differ if the phone and SIM card are changed?

An oath of divorce (yamin al-talaq) falls under the ruling of a conditional divorce. If the one who swore the oath performs the action sworn against, then divorce occurs according to the majority of scholars. Ibn Taymiyyah, however, held the view that an expiation for an oath (kaffarat yamin) is due if the husband did not intend divorce. In your case, if your wife speaks from her phone, divorce occurs. The ruling depends on your intention: Did you intend to prevent her from speaking from any phone she owns, or did you intend a specific phone and number? We advise you not to swear by divorce.