ことになる is used when a decision is made not by your own will but by an external force like a company, school, or circumstance. It often translates to 'it has been decided that' or 'it turns out that'. The focus is on the result or arrangement, not on who decided. For example, if your boss tells you that you will transfer to Osaka, you say 大阪に転勤することになりました (it has been decided that I will transfer to Osaka). This pattern is common in news, announcements, and explanations of situations. Note that the past form ことになった is very common when reporting a decision that has already been made. In contrast, ことにする (with する) means you decide yourself, so it's a personal decision. Use ことになる when someone else decides or when it's a natural outcome.