Default [Q] Replacing stock dialer on g2

Hello there, i have one (maybe stupid) question.
searched trough forum, but i didnt found answer on this.

on my lg g2, i like everything except dialer (in previous htc one x was much better ) so i decided to replace it with something from google play, i downloaded,installed, but problem is, that phone didnt asked me which one i will choose as default.
so now i have 2 dialers and everytime when someone calls me the stock lg dialer is showing.
(i tryed cca 6 dialers and restarted phone, but it never asked which one to set as main )
and i have no idea how set up the downloaded dialer as main. in aplications there is app called phone, but i cant turn it off or stop or something.
phone is not rooted and i will not root it.

on lg support answered me that they have no idea because phone must ask me which one i will set as main dialer.

thanks for any tip or help how to solve it.

ps: sorry for bad english.