Mexico roam like home doesn't work

I paid top dollar to have cell and data services in Mexico. O followed instructions and activated the service however I rarely had a working service.  I could make some calls but no data coverage.  I could make texts but no Web access.  Thinking it was a problem on my end.  I reactivated the service no less than 8 times hoping it would activate properly.  The roaming services acts like it is operational and I have been billed $240 for the 2 weeks, but it was absolutely useless in Mexico.  Can someone explain why I am paying for a non working service or did I require a special setup on my iPhone to make roaming work. In addition I would like the roaming charges reversed.  I await your reply