How To Block Unwanted Text Messages ??

I'm 3rd Party to the Problem, a Friend relies on his iPhone to get Important Text Messsages from his Dispatcher all times of the Day & Night... The Problem, somehow he is getting Text Messages in Group Form if you will (Everybody & His Aunt / Uncle) get the same message.. At the point of Annoying and Not Interested.. How can they be Blocked as there appears to be some form of road block if you will preventing Text from being Blocked.. Help Apprciated.. Cheers Thanks..