I guess this will come across as dismissive but The whole "they said and then I said and then they said" is just tedious. Maybe because I know what they said because it's what "they" always say to us. It's always the same questions.
If these people are your friends, and they continue to harass you about your atheism, then you can either 1) keep arguing with them, knowing you have as much of a chance of them changing their minds as they have of getting you to change yours 2) tell them to lay the fuck off, you're an adult, or 3) stop hanging out with them.
It's really that simple.
We have one life that we get to spend on this planet -- why spend so much time and energy around people who obviously don't respect you for who you are and the choices you have made in your life.
Imagine you're gay (and you may well be -- that's not the point) and your bowling buddies every day tell you about how much your life is lacking because you don't like vagina, and how awesome your life would be if you just got vagina in it. And then your other buddy says that how can you be sure you really don't like vagina, have you ever really given it a chance...
I call that bigotry. Just because it's sexual vs religious doesn't make it any different in my book.
So keep arguing with them, which is pointless, or find some people that will respect your views.
That's kind of the only advice really to be had.