Last month, the European Commission (EC) announced that it would be forcing Meta to allow third-party AI chatbots in WhatsApp for free in the European Economic Area (EEA). The decision followed Meta’s ban of third-party AI chatbots in WhatsApp last November, and the company’s subsequent move from March when it once again accepted third-party AI chatbots in WhatsApp, but only for a fee.
As a consequence of the EC’s decision, today ChatGPT is back on WhatsApp in the EEA. You can chat with it in WhatsApp at the phone number 1-800-CHATGPT, without needing to install the ChatGPT app.

Just like you would be using the ChatGPT app, you can ask it questions, upload pictures, send voice messages, generate images – everything is done within WhatsApp.
The EC’s investigation on this matter hasn’t concluded yet, but Meta has to maintain free access to third-party AI chatbots in WhatsApp until the EC adopts its final decision.
Via (in German)