How can I force my phone to connect to US-based cell towers only? I use a Samsung Galaxy S9 with Android 10, and plan to enter Mexico from the US via the land border. How can I force my phone to connect to US-based cell towers only? (I believe my data usage will get way more expensive for non-US data use)
It is currently impossible to do force one's phone to connect to US-based cell towers only. E.g. from Dicknose22 on https://www.reddit.com/r/AndroidQuestions/comments/j5ntyg/how_can_i_force_my_phone_to_connect_to_usbased/g7tefwh/:

Not to the best of my knowledge, even with total root access, your phone and the tower communicate on what to connect to you do not have power to override what your carrier decides you should connect to.