As for the frequency you are using, use the following guide to match your ARFCN (Absolute Radio Frequency Channel Number): "Network Operating Mode", if it is NOM 001 then Voice has higher priority (Class A), while NOM 002 indicates Data has a higher priority than Voice (Class B). Note that this Field Test Mode was disabled in i OS 4.0, and re-enabled in i OS 4.2.1.
However, many of field test features listed are no longer available unless you use an earlier version of the firmware, or re-enable via homebrew.
Changing cellphone, you can be tracked by SIM card used.
Note that this ability is similar to the assisted GPS feature of the i Phone 3G and i Phone 3GS, with the difference in that turning ON Location Services lets i Phone and its applications use this tracking info immediately (less than 10 seconds).
Turning it OFF means this tracking info from the cell towers is simply not processed on the i Phone, but is available if needed.
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That is why I have created a list of Top Cell Phone Spy Softwares 2018.