When was the "church" first mentioned?

I received some literature today with a few statements.. I thought I'd address the first one here. :)

Myth- the first mention of the church is when Jesus said he would build up his church.

Is that the case?  Did the "church" exist before then?   Let's go to scripture to prove this instead of just making this assumption.

- Ac 7:38 This is he, that was in the church in the wilderness with the angel which spake to him in the mount Sina, and with our fathers: who received the lively oracles to give unto us:

Here we clearly see the "church" mentioned in context with Mt Sina and Moses, This verse specifically calls Israel the church, well BEFORE Jesus.

Let's not just take pastors words for things!  Don't assume that just because a pastor wrote something "like this is the first time the "church" existed" that it's accurate!  search it out for yourselves!  See what the Bible has to say about things instead of the pastors!  

As another.. this same literature, as a way of REFUTING The sabbath says the BIBLE calls it YHWH's sabbath!  as a way of REFUTING the sabbath!!  Wake up my loved ones!  Open your eyes!  I love you and YHWH is calling for you!   This literature even admit's it's our heavenly fathers day!   Please Please.. listen!   search for the truth and pray!  He is calling you!  It says pentacost was important because it was a sunday.  Pentacost was important because it was PENTACOST!   Please, I beg and plead with you all.. awake!   We love you so much and it truly hurts our hearts that so many are blind to his words.