I suggest wearing one of these on your belt. There are numerous kinds made of different materials to match one's taste and situation (e.g. strict business models, sporty models etc)

Pros:

* Original post's problem is solved (fixing the phone in a particular position)

* You don't overload and overfill your pocket with a bulky smartphone

* Much easier to take out your phone while you're sitting (of course this may be bad because it might be easier to steal)

* Your phone doesn't contact other stuff in your pocket like change, keys etc that can damage it

* Normally those phone bags have extra sections for small accessories such as memory cards and batteries

Cons:

* Only if you don't like to wear stuff on your belt