They explicitly state that they will use your data to train. Here's the important line from ChatGPT's Terms of Use:
Our use of content. We may use Content to provide, maintain, develop, and
improve our Services, comply with applicable law, enforce our terms and
policies, and keep our Services safe.
If you type something into the internet now, or anything internet-connected that goes to a cloud service, it's safe to assume it'll end up in a training set, or otherwise mined for every last scrap of value, unless explicitly stated otherwise (and even then, it still might).
Adjust your behavior accordingly, if that's even an option for you anymore.
For most, it's not an option. Only 5% of adults don't own a smartphone, and there's very little you can do on one which doesn't feed the machine. RMS warned us this day would come, and now it's here. We've worked hard for this world, hopefully at least our masters will enjoy it.
Side note: It's partially because of this that if I type something into the internet now, I feel no obligation to not type the craziest and most schizoidal thing that comes to mind (this comment here is a rare exception). Might as well, since most of your audience is bots.