If you start at this web page: https://support.google.com/googlenest/gethelp and fill in a few fields to get through the usual attempts at diverting you towards places like this community, you can get to the "Contact Options" at the bottom. The best one is probably to have them call you, since you can avoid having to hang around on hold waiting for a support agent. But, you can call them instead, or use the "Chat" option.
That is puzzling. I went through that process myself to test it, and it seems to work for me. On that page, under "Please select your product family:" I selected "Wifi", and under "Tell us what we can help with:" I just entered "customer needs assistance" and clicked "Next".
Then I clicked "Other" and then "Next step" and then "Next step" again.
At that point, the "Step 3" contact options should appear. If you click "Get a call" you should be able to give them your phone number to have them call you, but "Call us" and "Chat" are both options as well.