Stop doing meth.
Look up the term RAT (Remote Access Tool) and how to find if there is one on your device and how to remove it. But if you want proof of this happening, leave it on your device. Research the brand or company associated with producing the software and find out who they usually market to. If the software appears custom, this may be government, or more likely govt contracted. If it's Pegasus software, (or even if not) contact the company (in Tel-Aviv) which designed and marketed it. If you believe US Law Enforcement or US Govt has something to do with it, allow foreign sources to remotely access your device and check it out or install tools. Sounds crazy and unsafe, but foreigners on your phone are indifferent towards you, and won't care about anything but "analyzing" the American govt software on your device and "analyzing" the contractors or agents who are tracking you.
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