"We call on ADP to stop making life more difficult for small business customers and live up to its corporate value: “integrity is everything.”"

See: Twitter, Facebook, and even Google. All of these companies have destroyed 3rd party companies by basically using them as a test base for new ideas and features and then directly competing (and many times, cutting off the 3rd party completely).

If you are going to base your entire company off of a 3rd party, you better have a plan B if they completely cut you off.