Why does my car have a long lag while shifting?

What is your question?

I've been down to the dealer 4 days. The 1st time they serviced the transmission, they told me to drive it over the weekend and I did. I brought it back in on Monday and they reset the computer module. It drove fine, then it started shifting weird again and would rev really high. Brought it back in, they have kept my car overnight 2x's. They can't seem to find the problem. It shifts weird when it's cold and now has a long lag between shifts. I just bought this car a lil over 30 days ago and it only has 60k miles on it. I'm frustrated and I have an after market warranty on this car and no one is providing answers. This happens intermittently as well. I'm over wasting my time, energy and gas.