here is the deal.
everyone has the sms/dialer phone app on their Xoom. if you go to applications 'all' you will see the phone icon app/dailer
DSG is rooted, hence access to the hidden app, but gsm radio/data plans do not give access to sending sms/calls. the Xoom lacks a voice plan/required hardware, hence it cannot make voice calls/send sms.
this can only be accomplished via voip apps
DSG hasnt a clue, and will never get satisfactory resolution