otrmobile.com - low price though price has been increasing this year, they’ve started throttling video on AT&T network (can circumvent with VPN), recently ended T-Mobile option, allows you to use your own modem.

neverthrottled.com - more expensive, only uses AT&T network, allows you to use your own modem, no throttling.

4gdata.net - offers AT&T, T-Mobile, and Verizon service, limited availability, only AT&T allows you to use your own modem, no throttling.