If you can, turn off unknown callers from being able to reach you.
I’ve done this and it’s been wonderful. The spams have actually decreased significantly since I don’t answer the phone for them at all anymore.
It’s under Settings > Phone (have to go into Apps in iOS 18) > Silence Unknown Callers
Anyone who is not in your contacts gets a ring but the ring doesn’t go to you so you don’t hear it and don’t answer. They can leave a voicemail but scammers never leave me voicemails.
Just need to make sure it’s not doing some phone home stuff after the fact, or cut it from ever reaching the Internet at all. I wouldn’t put it past any big corporation to be pulling that with the guise of the app being local and double dipping by selling data at a later date.
Linus Tech Tips did a good job exposing Anker for doing this with security cameras that were supposed to be local only but were found to be uploading pictures to their servers.