with yext, after you fix it and cancel their service, will they change your listings back to the incorrect format or no?You can submit changes to Yelp directly I believe and Hotfrog is updated with info from Localeze.
Basically you can use a paid service like Yext or Synup or you can submit changes to the data aggregators like Localeze, Infogroup, Factual, etc. and the sites directly.