To REALLY save money, coverage is always a consideration. It doesn't surprise me that he thinks this. Sprint and T-Mobile are the biggest examples. They are fine in most Urban areas (And a few rural ones.) but for the most part their coverage is worthless if you travel a lot. (I have a Spring MVNO and am perfectly fine with it.)
You're NOT saving that much money!The TRUTH is you are NOT saving that much money. I'm sure you've seen information here and other places, but I'll mention my costs for clarity. I use Tello , which is a true pay as you go. I paid $10 to start my service 8 months ago and still have $8.XX remaining. Yes my total cost has been less than 25 cents per month! Well that isn't a fair comparison because I only use my Cell Phone briefly in the car. I use Google Voice (Hangouts) for the Majority of the calls I do make. (It does have occasional lag, but is usable and my Cell rings just like an ordinary phone when someone calls. You can see I don't place much value on my phone usage. Your SO will have very different needs.
A plan that matches your (Their) needs
You do have to pick the right place and also make sure your plan matches up with your needs. I have Wifi the majority of the time, so I Keep the cellular data turned off on my phone which is a huge savings. (Calls and Texts still work fine! That's what my phone is for!) If you know AT&T works well for you, you will go a MVNO for AT&T. They will typically tell you, but if unsure you can find them on the following list: (The two companies you picked use AT&T Towers.)
https://en.wikipedia.org/wiki/List_of_United_States_mobile_virtual_network_operatorsWhy:First explaining by store fronts make no sense. The truth are these companies are making a ton of money. So first and foremost these smaller companies are making a smaller profit?
Why do all the companies "allow" MVNOs to exist in the first place? It's genie in the bottle situation. Say Verizon is the only company that sells its service to MVNOs. Verizon makes a killing by selling service to both directly to consumers as wells as to whole sellers. ShareholdAT&T, Sprint, Etc. simple wouldn't be able to compete and hit earning expectations in that environment. The only option is to do the same thing! From the consumers viewpoint I would compare this to buying the Kroger brand. The Kroger brand is almost identical in most instances. But you know Chocolate O's are not going to be as good as Oreos. (It just simply isn't possible for some reason.) - Don't buy Chocolate O's unless you are someone willing to make that trade off.
Example: My Father lives out in the middle of nowhere. Coverage there is spotty with many carriers.For his location AT&T has Okay coverage and Verizon is the best. My father purchased phone service with Page Plus. (Verizon MVNO). He gets excellent coverage.
Biggest thing to remember anytime you change service:
Do not cancel your old service until your number is fully ported to your new service. If you want to keep your current number, porting can be the biggest challenge. It takes patience and a 1-3 calls to do so. You basically have to give the new phone company your consent and all your account information from your current line. Essentially AT&T (And every other company) wants to keep you as a high paying customer. They are only going to release your number to a competitor if the paperwork to do so is perfect.
- If you cancel your current phone service without porting your number, then your number is gone forever.
Source: I've had plans with every major carrier and a number of small ones. I managed the devices and phone service for a mid-size company.