What carrier options do I have for my Moto X?

Episode 1230
Bill fromBill's cellular provider is CDMA and he's losing the ability to use his Motorola Moto X. Leo says that the good news is that everyone is moving to LTE/VoLTE, which means CDMA will disappear. Even now, when going with Verizon, you can see the phones have GSM SIM cards. But the older models won't work anymore. A newer one will likely work. Leo says it's time for a new carrier and T-Mobile would let him bring almost any phone to them. T-Mobile also has a pay as you go $30/month plan.