Sim Card not supported.

Today, I transferred my iphone 8 plus to cricket from straight talk. Before I transferred I was guarreeted that my service would transfer with no problem. Once I transferred my sim card would not support. I ask the lady what was I going to do and she said that there was nothing that she could do. I paid 90 dollars today. I still currently do not have a phone. I am VERY UPSET about this issue. My wife is 8 months pregnant and I have to have a phone. Does anyone know anything that I can do? I have tried to get in touch with someone to just give me back my money since it would not work but I have had no luck. I dont mind trying out anything new but if it dont work I should be given back my money. I need a phone.