Any intelligence agency can target your device with malware that will give them full control. The primary defense you have against this attack is keeping your device fully patched and updated. The attack could target the messaging software on the device, the mobile Operating system, or even the cellular circuitry before it reaches the Operating System! Thus, the choice of operating system does not matter if the phone hardware has a vulnerability in its low level firmware.

GrapheneOS has additional hardening over the open source Android, and also implements fixes from Android; But it is not immune to this attack. It is just as important to keep it patched and up to date.