I have an iPhone SE, When I get an incoming call (I've just called myself to check, and there seems to be 2 types I get!)
- one is the red and green button phone buttons, so press the green one to answer and red to go decline;
- the other is the green phone button a on white background which you swipe right
No idea why they were different either, ring myself twice from my Alexa! Weird ....
Maybe take it back to shop if it continues? Good luck!