Phantom private number calls

I received a call from a private number that I did not answer. Looking at the call logs later on let me know that the call in question lasted 22 minutes and 7 seconds. This is not the first time this has happened to me while using this phone and number. I need the likelihood of this occurrence happening multiple times, no ringing; not answered; long call duration. Or the alternate possibility that someone has put a program on my phone allowing them to call and listen in via my phone's microphone remotely . I first checked on whether or not this is even possible and found a few sites claiming to offer just that sort of service. Perhaps this is a just my paranoia but at least someone else telling me that is the case would help me to relax lol.

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Sorry forgot somehow to input my phone specs. SAMSUNG-SM-G890A not rooted, running Android 6.01