I only have a cell phone. Obviously I know who’s calling me 90% of the time, and generally answer the phone with a greeting like “What’s up?” or their name.
If it’s somebody from work I answer with the usual “Hello?” even though I know who they are. They’re not friends of mine so they get the more traditional greeting.
And if I don’t know who’s calling I simply do not answer the phone. They can leave a voicemail. Talking on the phone with people I don’t know makes me somewhat irrationally nervous. Like I’ve answered the door in my underwear or something.
When I call my friends, they generally acknowledge that they know it’s me. This doesn’t bother me at all. It’s not like I don’t know that they have my number programmed in their phone.