[Tinc27]

I have a galaxy s3 i535 running kitkat 4.4.2. I rooted it using towelroot. Ran root checker. It said it was rooted. Downloaded twrp and ran that. Now the problem. twrp asked about the install partition. I agreed to where it said. Then no twrp screen. So I tried to boot into recovery and a screen came up saying "samsung custom with an open lock icon" and then it switches to a screen that says system software not authorized by verizon wireless has been found on your phone. Please turn off your phone and go to the nearest verizon store for help ". Verizon is no longer my carrier. I am now with another carrier with a different phone. So as you can guess I was trying to install a custom rom. If I hold down the volume rocker, hold the home button and press power it boots into the phone mode. All my icons are still there. I can use wifi. Don't know if it will call out as I don't use verizon anymore. Where did I go wrong. Please help. I would like to install a custom rom if possible.