Fuel Injectors

My car has been having fuel injector issues. This is the third time in 6 months. I get told that they have replaced the injectors every time. what prove do I have that the injectors have been replaced? can they not do a proper check on what keeps on damaging the new injectors (that's if they are new). This is really frustrating as I travel with my kids on a daily basis and always having the fear that we might get stuck one day due to this issue kills me. Please help. I am really frustrated.