There is usually no real human behind a robocall, only an automated, pre-recorded message. Many types of robocalls are legal, as are emails, SMS/MMS, and phone calls, but they can be abused. A new trend involves the use of numbers with the same area code and first three digits of her own contact number. Ailsa Chang, a correspondent for NPRs Planet Money podcast, documented her experience with this when she received a call from a number.”]
Source: https://blog.malwarebytes.com/101/2018/02/stop-telephoning-me-robocalls-explained/