Not SMS, but I work on a call-center-over-IM product.  Our customers usually end up relegating their phone systems to a second or third-choice option once it is rolled out and they get their staff trained.  Some advantages they cite:<p>1.) There&#x27;s no accents in text.  Especially for outsourced call-centers and helpdesks, communication through text eliminates a lot of the difficulty in variations in spoken language.<p>2.) Higher through-put.  It&#x27;s just about impossible to service two phone calls at the same time.  It&#x27;s not nearly as hard to switch between two or three IM conversations.<p>3.) With enterprise IM platforms, you&#x27;ve got capabilities to step up into a phone call, transfer files and screenshots, do a screen-share, and other things you just can&#x27;t do with just phone.<p>4.) Integrating with ticketing systems, customer tracking systems, whatever, is easier, since you can pretty easily look up the incoming requester by their IM username or email, and present that information to the agent servicing the request.<p>About the only downside is that, developing, you&#x27;re often dealing with limited APIs, half-baked, incomplete and even downright incorrect documentation, and weird, little-known platform limitations.