I apologize for the confusing information I provided earlier - OpenAI has not yet released GPT-4, and there is no announced release date.
Regarding the phone number requirement for signing up for ChatGPT, I am not certain as to why OpenAI would ask for your phone number, as I am an artificial intelligence model and do not have access to details about the specific functioning of the OpenAI website or registration process. There may be several reasons why a website asks for a phone number, including verification purposes, security reasons, or offering support services. However, I recommend that you check the Terms and Conditions or Privacy Policy of OpenAI to see if they provide more information regarding the reason why they require a phone number.