A large part of the internet is blocked in mainland China. All Google services (Search, Gmail, Maps, YouTube), Facebook, Instagram, WhatsApp and most Western news outlets are unreachable, as is virtually every adult website. If you need any of these during your stay, set up a VPN before you arrive — the VPN providers' own websites are blocked as well. Two reliable commercial options are NordVPN and Astrill, which has specialized in the Chinese market for many years.
For a short visit there is a simpler alternative: mobile data roaming on a foreign SIM card or a travel eSIM is routed through your home carrier and is not filtered by the firewall. It costs a little more, but it works out of the box with no setup at all.
At the time of writing, this website is reachable from within China without a VPN.
WhatsApp has been blocked in China since 2017, and in any case almost nobody in the country uses it. Chinese daily life runs on a domestic app called WeChat — chatting, payments, taxis, everything. If you want to stay in touch with local people, which includes contacting most independent escorts, you will need a WeChat account.
WeChat itself is a polished, easy-to-use application. Its built-in translator makes conversations with people who speak no English perfectly workable, and it handles pictures, short videos and live location sharing. One thing to keep in mind: WeChat accounts are tied to a phone number, and Chinese phone numbers are registered against a passport and address — so treat nothing on the platform as private. With a foreign number that concern is considerably smaller.
You can get WeChat from the App Store or from Google Play.