Help getting on track

I have a huge problem. I had a Verizon s4 that I was using on straight talk at&t. It wasn't working great. It kept getting stuck on an lte signal and not letting me send text messages, so I decided to trade someone for a T-Mobile one. When I got the T-Mobile one I decided to root it and put on a stock lollipop rom. Now it says that my sim card isn't there. Nothing i do works. I have tried flashing back to a 4.4.4. Tw rom and still nothing. I have tried to flash a modem with odin and it keeps failing. I am trying to flash back to stock with odin and it keeps failing. Please help me!