The thing is that today you dont even need access to the coversation when you have metadata. Imagine, a woman calls a number of center for planned parenthood, is on the phone for 20 mins. Then she calls a number of her gyno doc for couple mins. Then her phone is located at that gyno doc a week later for 2 hours or whatever it takes. Do you need to decrypt the conversation? You already know what was discussed.
Do you really not have prepaid sim cards in the US? that you buy with 5 bucks and it lasts one year, and then you just top it up for another 5? Those carriers are really milking you good over there.