Just be glad you don't have RingMaster Service as well. One of AT&T Jewells. It's an extra incoming calls only phone number. Most telemarketing calls are ROBO Calls meaning a computer dials the number and if you stay on the line or press a key the crooks come in the line. Two numbers means twice as many calls. It doesn't matter if your line is private because they call every number in the pre-fix like 687-1111 next call will be 687-1112 and they call up to a hundred at a time. Actually likely 1000 but spread out over a few area codes. The phone companies lease the telemarkers these lines they can't claim innocence.
AT&T & other Bells, FCC, & FTC all know darn good and well who is doing this stuff and make no effort to stop. The phone companies rip people off with selling extra service to residential customers to buy for privacy then allow the telemarketers to violate that as well. A win/win for the phone companies. Ma Bell used to crack down on harassing calls and took it serious.