I get only 5 digit phone numbers once in a while on my cell phone. What does this mean?

I think people may be listening to my cell calls.I always hear a series of unique beeps when I'm on the phone.I get only 5 digit phone numbers once in a while on my cell phone. What does this mean?
You're paranoid, it's kind of scary actually. Get out your tin foil hat.





Because this conspiracy is just the tip of the iceberg. You know those 5 digit numbers you have on your phone?.... They're from companys that you've subscribed too! OHHHHHHHHHH NOOOOO. Either that or you used your cell number as a contact number and it was sold to a company. Text STOP to that number, your paranoia days are over.