I have to keep blocking calls manually how can we stop them automatically
I suspect a bunch of the spam calls are coming from spoofed numbers, which is why blocking a specific number doesn't work, because the spammers will change the spoofed number every few days. There is no real surefire way to get rid of all spam/junk calls and texts, but you could try a 3rd party app if this is a mobile line. Otherwise, the only other thing I can think of would be to set your phone such that it blocks all calls from anyone not in your contacts list. That can obviously be problematic if an organization or business you regularly deal with uses an automated service to send you reminder calls or texts.
If it's a landline, here's an old thread with one solution to cut down on junk calls:
STIR/SHAKEN to prevent caller ID spoofing - verizon
Also, opt out of 3rd party marketing with any businesses you deal with, and don't display your contact information publicly on any social media. Here's a thread on how to opt out of 3rd party marketing associated with Verizon:
Verizon sells your info to third party - how to opt out - verizon
