They are not required to suggest you delete their account in their chatbot.

But you have to be able to prove who you are. I can't just ask for any old phone number to be deleted.

In any case the instructions don't say to lie about it, so this seems fine either way.

Bullshit.

  Recital 64: The controller should use all reasonable measures to verify the 
  identity of a data subject who requests access, in particular in the context
  of online services and online identifiers.

Yes someone drools out this particular version of "because GDPR!" enough I know exactly where to look for the rebuttal.