If pipe has been frozen for a week, should I call a plumber?
I would only call a plumber if the purpose was to have the plumber reroute the lines to an interior wall where the pipes will not freeze.  I can't see paying someone $100 an hour plus for holding a hair dryer or mini-blow torch next to a pipe to get it to thaw.  Your plumber plumbs not perform magic.  

If your pipes are freezing to this extent though I think that you will eventually need to have things reworked.  Spend your plumbing money on this.