Which MVNOs work with more than one carrier?

Signing up for AT&T, Sprint, T-Mobile, or Verizon service is making a commitment to a network. MVNOs just sell access to one of the major networks with different services and plans that might work better for some people. Most of them ditch any sort of contract as well. Unless an MVNO is partially owned or operated by a specific carrier, it will have no specific commitment to any network.

With an MVNO, it can be possible to choose which network works best for you or use one that's compatible with the phone you already have. Keep in mind that if you roam a lot or see extended LTE popping up on your phone, you're using another carrier's network and you may lose service in these areas on an MVNO.

Just be sure to check the coverage map for each carrier before signing up.

Sprint and T-Mobile

In April 2020, T-Mobile completed its purchase of Sprint taking over all of its network assets. While this will undoubtedly have an eventual impact on MVNOs making use of either network, for the time being, there's no set timeline for major changes.

If you use an MVNO that uses both Sprint and T-Mobile, you will only have access to that one network. Some MVNOs have roaming agreements in place but you will still connect to the primary network if at all possible. The only exception is Google Fi.

Automatic switching

Google Fi is unique in its ability to make use of three networks in the United States simultaneously with no input from the user. There has been a lot of work behind the scenes to make this work correctly and still only works on select phones. Still, if you need the coverage offered by Sprint, T-Mobile, and U.S. Cellular, Google Fi is your best bet as long as you're willing to use the right phone.

The networks

Many MVNOs allow you to choose, or choose for you, the best network for your area or phone. One of the main reasons is that people will be able to use nearly any phone they buy with at least one of the MVNO's SIM cards. This can be a huge benefit to someone trying to save money buying used phones that may not support as many networks as newer high-end phones.

These are the carriers that have access to multiple networks.

There are quite a few good options but keep in mind that you will need to make sure you check the coverage for the carrier you intend to use as well as phone compatibility. The most important factor is making sure a carrier has coverage where you need it to. Still, having the flexibility to use nearly any phone with a carrier can give you a ton of freedom and help you save a lot of money.