While all good points, they don't specifically address the problems mentioned in the post.

Douglas Leith, a computer science professor at the Trinity College Dublin, claims in his "What Data Do The Google Dialer and Messages Apps on Android Send to Google?" paper that Google's Messages and Dialer apps have been sending data to the company's servers without taking explicit user consent. More specifically, these apps collect information about user communications, including an SHA256 hash of the messages and their timestamp, phone numbers, incoming and outgoing call logs, call duration, and length. This is then shared with Google's servers using Google Play Services Clearcut logger service and the Firebase Analytics service. The data helps the company link the message sender and receiver and/or the two devices in the call, enabling features like spam filtering and business caller IDs. - similar report from Android Police

The quickest/easiest thing to do to mitigate any risks from the accusations is to just use a more privacy friendly SMS app and phone app. However, doing so may lead to some unwanted outcomes (eg - no RCS, loss of phone call functionality that Google has implemented over the years) and it may not eliminate Google's ability to collect this information anyway due to Google Play Services. These are small prices to pay and aren't difficult to adjust to if you're concerned with Google abusing or mishandling your data.

An even better quick win would be using private and secure messenging, calling, and video chatting services instead of traditional SMS and phone calls. There have been a few mentioned in the thread. Doing so may be frustrating as you'll have to convince everyone you communicate with to use the app(ss of your choosing and you'll likely run into situations where using those apps are not possible (eg - school/work activities, interacting with businesses, etc.).

Aside from not using a cell phone at all, the best thing you could do is ditch traditional Android (ie - Android with Google Play Services, the Google Play Store, etc.). Moving to iOS may help mitigate Google's data collection ability, but it shifts the risk from Google to Apple. Instead, as /u/Jouissance_juice mentioned, using GrapheneOS would help tremendously with the recent accusations (in addition many other privacy and security risks). The downside is that it requires a Pixel phone and it can be a bit of a jarring experience for people who ate used to the ttraditional "Google" Android experience. There are other ROMs (eg - CalyxOS, LineageOS, etc.) that may offer a less jarring experience at the expense of a (possibly only a little bit of) security and privacy. Keep in mind that even if you do this and still communicate over SMS and traditional phone calls that the carriers and others (including Google if the other person you're communicating with uses Android) will still be able to access most of the information as before you made the change. You would still need to move to a private and secure communication app to mitigate your privacy concerns as much as possible.