William Buffy work for phone s-e-x agency and take tandem calls

Buffy has kid
Dawn is Spike's sister who is looking at a college in Buffy's location
Liz and William try to make each other laugh on the calls
Spike and Buffy are characters used on the phone
Andrew and Faith are mentioned as return callers
Liz and William had never met but like each other before Dawn's college visit
Buffy moves to Spikes location in the end

That's one of Kantayra's stories.

http://archiveofourown.org/works/219156/chapters/329788

There's the link. Enjoy

Mji818
The fic you are looking for is by Kantayra and it's title is Touch Me. You can find her fics at Elysian Fields and Sinister Attraction.

Hope this helped,
UncagedMuse

Thanks! I knew that it was popular enough that it would get a response, but darn if I could find it in a search. Spuffy, or any other book for that matter, I always forget titles. I'm sure that says something about me, but I probably don't want to know what! ;P