What Robert in his last two paragraphs...
And what lucy24 said in her first statement... We were posting at the same time.
C.) None of the above.
Find a way to 'engage them' in something else, either before or even possibly after letting them read about the service that is no longer available with something like 'although this specific service is no longer available and there's not a direct alternative we've found, you may be able to combine [blah], [site] and [service] to work for you or you can continue looking for something else that fits your specific needs on our page [here] if those don't meet your personal requirements ... If you know of a direct alternative, please feel free to <link>contact us</link> with the info and let us know, thanks!'