You know how I know someone has an Iphone?

I get a spam email from their Apple email.

I get double texts from them.

They tell me their texts don't work sometimes -seems like a SMS issue.

They'll tell me they did not get my text when my phone shows it was sent.

They can't receive pictures from me in texts.

They try to blame Google Fi or Android for the above when I know it is the settings on the Iphone.