How should I handle poor English in reviewing an article that claims to be proofread by two native English speakers? I was asked to review an article written by non-native English speakers. I had never seen this before, but the manuscript includes a link to a certificate from a website called Textcheck that says:


  We hereby certify that Textcheck has checked and corrected the English
  in the manuscript named above.
  
  A specialist editor with suitable professional knowledge (M.Sc. or
  Ph.D./M.D.) reviewed and corrected the English. An English language
  specialist subsequently checked the paper again. The first language of
  both editors is English.


Unfortunately within the first few pages I'm already encountering clauses that make it obvious that this was not done to any depth. The issues are so blatant that even a quick glance by a native English speaker would catch them.

Should I point out major grammatical errors such as these in my review? Should I comment to the authors that they essentially got ripped off by this service (in more polite terms, obviously)? Should I comment to the editorial office?

EDIT: I also see that I can email Textcheck about the article. Should I do that? If so, what should I say/ask?
You should not email Textcheck about the article. The journal review process should be confidential, and you should not take the liberty to violate it. You should put the quality of the writing in your review. If it's still bad even after review by this company, then those are the breaks. It sounds like it still needs some help.