I have Kerrit breeches with side pockets and my phone hasn't slipped out once! They have no zippers or anything either.
I also use a bum bag. It's perfect for your phone, keys, riding gloves and so on
I just ordered a pouch from Amazon that goes around the waist. I plan on wearing it under my tshirts when I ride. It's called the Flip Belt waist pouch. Designed for lathered and runners for keys, phone, etc.
I use a phone holder but some of my saddles have d rings so I used a holder that my mum gave me to clip on them
I use one of these phone holders you put on the arm.
I just put on my arm like a running phone holder. I saw on a gp that they are doing them for the riders originally and you can put your holder on your breeches under your show jacket. And it seemed to be great! But i dont know from which brand it was :/
I use a bum bag (you can hold both your phone and keys)
I just put mine into the pocket regardless of whether there's a zip or not! I shove it down as far as I can and angle it so it won't fall out!