Makes perfect sense. There are MVNO dealer/resellers for all the major networks. Each MVNO offers the same network (towers, etc.) for a lower price than the brand name. In my case, I use Cricket which is an MVNO on the AT&T Network.
The distinction is:
1. You must have a paid-in-full unlocked phone. MVNO's don't deal with subsidies or monthly phone rentals.
2. You must read the fine-print. The TOS (terms of service) are different than the underlying name-brand. For example, Most MVNO's do not allow ANY roaming outside the US whereas named carriers have either a la carte roaming (at very high per minute rates), or roaming plans with lower, but still expensive rates. Because of T-Mobile, more named carriers (and even some MVNO) are starting to offer free or lower-cost roaming to US/Canada and even other countries. In my case, Cricket just added Canada/Mexico free roaming which was a pleasant surprise.
3. Bandwidth caps and traffic shaping - MVNO's will often cap LTE at lower max speeds. e.g. Cricket limits me to 8 Mb LTE speeds which realistically is faster than I would get anyway in most areas and much faster than 4G anyway. StraightTalk, and other MVNO's have fine print that say they can throttle your traffic if the underlying network is congested.
4. Billing and customer service - MVNO's use the name-brand towers and radios, but customer service, billing, and support are all roll-their-own and often inferior (to keep their costs down).