Where the private handset ends
GrapheneOS changes the phone. It does not turn Telstra, Optus or Vodafone into an invisible network.
Your mobile account
If a SIM is registered to your account, the telco retains the account relationship and billing records that apply to the service.
The boundary to keep
A private handset changes the device. It does not silently rewrite the records created by every network, provider or account around it.
Network connection
Mobile networks necessarily process connection and cell information to deliver service. A hardened handset does not remove that network layer.
Starlink and Wi-Fi
The phone can connect to Wi-Fi supplied by Starlink or another provider. That changes the access network, not the fact that the internet provider and services you use may create records.
What PRIVATEPHONE changes
The phone can reduce privileged Google access, tighten app permissions and separate activities into profiles. Treat the network, accounts and delivery as separate privacy decisions.
Check the phone against your real life
The exact bank, identity, work, vehicle and messaging apps matter more than a general promise.