Why are Mobile Phone companies gives authorities to the customers various number can calling.

Sir, I have received some mobile massages and phone call from a company various numbers. The number has call me by various numbers and harrasing me, some call I have revived and some massages was I have delete from my device also the company has massage me in my device innerly it has shown in front screen. I confused hare how can the apps has gives their information in front screen. I have Emil I'd phone no for network and trusting by phone calling or SMS. The SMS is came to without phone no. I trying to understanding, it has sending me by computer or other devices. The SMS some code wards or English characters and Some SMS are Six- Seven figures. I have no experience about this types of mobile no.So,how can mobile companies has gives the sim card or phone no. to an individual, the mobile companies always distributeb SIM after submission the addresses prof and actual identity for an individual.