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Certainly helps to report them - it goes into Apple's spam filtering. If they're iMessage instead of SMS, they'll cancel the iMessage account too.
They don't cancel anyone's iMessage account, they actually block it to prevent sending anymore messages. If that person contacts Apple Support regarding the block, a Senior Advisor can confirm the block and remove it for the account holder.
 
They don't cancel anyone's iMessage account, they actually block it to prevent sending anymore messages. If that person contacts Apple Support regarding the block, a Senior Advisor can confirm the block and remove it for the account holder.
Semantics.

They can unblock it to a point. If the behavior continues, it's locked out totally.
 
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