Skyway I don't think this is possible to do in GrapheneOS, but perhaps you could find a mobile provider that only provides calls?
Nevertheless, I think OP shouldn't worry about this. First of all, this article is outdated and the exploits mentioned in the article have likely been patched long ago. Second of all, the government wouldn't use such an exploit indiscriminately on civilians, since they don't want it to be discovered by researchers and the like. Unless you are a target of the government, this type of exploit should not be your primary concern. Lastly, both phone calls and SMS are highly insecure. If there is an exploit that works over SMS, there's probably also one for calls, so it's better to turn on Airplane Mode.