Got two sim cards shipped to me for free, and went with the one my phone was compatible with (GSM LTE). I chose the 5GB plan with US Mobile. I had to "port" my number from my previous carrier, Sprint, to US Mobile. At first I was confused and my cell/messaging wasn't working, but a quick chat with customer service fixed it. The rep finished porting my number and my calls/messaging worked afterwards. I noticed my data wasn't working however, so I did have to contact customer service via chat again, but the issue was resolved within half an hour and the rep even answered several other questions I had about the difference between the sim cards, CDMA vs. GSM phones, 5G coverage, etc. So far it's been a great experience :)