Actually, no, they wouldn't. You using a feature of their phone (but they're still getting your regular subscriber fees) without hitting their network is a win/win for them.
You seem unwilling to acknowledge the fact that inclusion of the chipset doesn't mean the same as having a radio built into the phone.
To better illulstrate - for years the chipset providers included support for GAN/UMA (now known as Wifi calling or VoWIFI) in their offerings, but the handset makers didn't enable this feature until it became popular to do so.
It's typical that chipset manufacturers include features early...to give the handset manufacturers the capability to try out features in their research departments long before they put them on the device roadmap. (and, even then, they may not end up on the roadmap if there is no business reason to do so). If a feature "dies on the vine" -ie isn't picked up by any of the manufacturers, it would eventually get dropped by the chipset manufacturers as they developed new chipsets.
You can't assume it's just turning something on....if a handset has a feature, you can bet your **bleep** the handset manufacturers want to turn it on and have you use it - it differentiates them from their competition and allows them to sell more handsets.
