A carrier bundle is the operator-specific settings package Apple delivers to iPhone that switches network features such as RCS messaging on or off for that carrier's SIM.
A carrier bundle (also called a carrier settings update) is a small configuration package that Apple distributes to iPhone for each mobile operator. It tells the device which network features that operator supports: VoLTE, Wi-Fi Calling, 5G modes, Visual Voicemail and, since iOS 18, RCS messaging. The bundle is tied to the SIM or eSIM, not to the iOS version, which is why two iPhones on the same iOS build can behave differently: one shows an RCS toggle in Settings, the other still sends SMS only.
For business messaging this matters more than any feature list. RCS for Business only reaches an iPhone when the recipient's operator has an updated carrier bundle with RCS enabled and has connected its RCS infrastructure (usually Google Jibe or its own) to the RBM ecosystem. Apple publishes the resulting per-country list on its "Wireless carrier support and features" pages and updates it without announcement.
Example: in September 2026 an iPhone on EE in the UK receives encrypted RCS in beta, an iPhone on O2 receives standard RCS, and an iPhone on Vodafone UK receives SMS, because Vodafone UK is not yet listed. A CPaaS provider handles this by running an RCS capability check per number and routing non-RCS iPhones to SMS through cascade routing.
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