Slingshot will be changing all users on FS/128kbps plans onto there new Express Plans, HS/HS 10GB and free offpeak data 6am-8am and +$10 if you don't have a homeline with Slingshot.
HS = High Speed and replaces the Term FS = Full Speed
This change is a kick in the pants for many of Slingshots existing customers who will be paying more for 5GB less data and 4 hours less free off peak data.
They are blaming there provider Telecom for the changes.
http://forums.slingshot.co.nz/viewtopic.php?p=49320#p49320