How to answer the doorbell on the app.
Welcome to the Forum, @robertrbunce! 
I don’t have any experiences with using the Wyze app on iOS, and I’m not sure which model of doorbell you’re using, but I hate to see your question hanging out here unaddressed, and I hope that someone with relevant experience can contribute a good response for you.
I’m using a Wyze Video Doorbell v2, and when someone presses the button, I get a notification on my Android-based phone that I can tap to answer. In the Wyze app, there’s also an option to enable Voice Over IP Calls (tap Account ➜ Notifications ➜ Push Notifications ➜ Voice Over IP), and that’s supposed to trigger a phone call instead of a regular push notification whenever the Doorbell button is pressed, but I haven’t spent much time playing with that.
If you can let us know which video doorbell model you’re using, then we can ask a Moderator to update your topic tags, and possibly that would help us get some better visibility for your question and find you an answer.
Thank you for responding to my question. I’m using the Wyze video doorbell v2. When we get a notification on our phone or iPad that someone pressed the doorbell,
we press the notification. Then what? The app is confusing. How do you exchange in conversation?
It’s been a while since I’ve used that feature. Unless someone else answers with a description, I might have to recruit someone to help me test it.
I should note that I’m not a Cam Plus subscriber, so the only notifications I get from my Video Doorbell v2 are generic sound, generic motion, and doorbell button presses.
Whenever someone presses the doorbell, I get a notification that someone is calling (I think; I’m doing this from memory at the moment), and I can tap to open the notification and then tap within the notification itself if I choose to answer the call. Then I can engage in a video call with whoever is at the doorbell camera at that moment with 2-way audio (between doorbell and phone) and 1-way video (from doorbell to phone). It’s like watching my phone screen and doing a speaker phone call with someone, holding the phone away from my face.
I think the VoIP option acts more like a regular phone call (without the video), but I’m not 100% sure about that—again, going from memory.
Since you mentioned that you’re using Video Doorbell v2, I have asked the Moderators to update this topic’s tags, so maybe that will draw other users of that product in to provide additional input—hopefully someone who actually uses iOS!
Edit: I didn’t pay enough attention to try to determine what kind of phone/operating system is being used, but this reviewer (starting at about 7:16 in the video) demonstrates answering a button push notification on his phone and also responding to someone else pushing the button so that he can take the call and use the 2-way audio:
