Player asks me to lock in their champ then takes my role and forces me to Supp

I got into champ select and my supp asks if I can lock him in yummi, He then locks in Akali w/o asking what adc I'd like. Then types in chat "I am adc now" And refuses to swap champs with me. What do I do here when I am at 0 lp? risk the demote from the dodge? Or play it out thinking since its my first loss on 0lp I shouldn't get demoted. Long story short the Akali was NOT good at akali and actually missed his ult multiple times, we lose because I am on yummi and I cannot carry even though I have more gold than Akali. Tell me how I am supposed to avoid these players?