If Mom bought the phone and is paying for the connection, then the phone is hers, and she has every right and reason to dictate how it will be used.
But if the OP bought the phone, and is paying for the connection without any help from Mom, then Mom does not own the phone, and the OP has every right and reason to expect privacy.
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The mere fact that science may not yet adequately explain an object, event, or experience does not mean the immediate explanation should automatically default to a conspiratorial, extraterrestrial, paranormal, or supernatural cause.