I grew up in New Jersey, and when I first got a cell phone, T-mobile was using a brand new area code in NJ, 848, which was the area code I received, and I have yet to meet another person with that area code. A good reason for that is that I moved away from NJ not too long after college.
Telemarketers can spoof phone numbers, and tend to like to pick one that match the number they are calling, or sometimes a neighboring area code to that area code.
This makes it easy to block the vast majority of them since I don't get calls from that area code, and if you are getting a new phone number, I would recommend doing something similar. Choose an area code where you are extremely unlikely to receive calls from it (maybe Alaska), and then get a good call blocker tool.
I have android, and unfortunately the app store kinda sucks now with everything being ladled with ads or subscriptions or both.
I side loaded f-droid, which is an open source oriented app store which has lots of free apps that are not abusive. I am using this one which has blocked hundreds of spam calls, and allows for wildcard area code blocking: