Hi,
You should recheck clients are taking updates from SEPM or GUP?
Make sure remote clients are set to pull mode and heartbeat interval is set to 30 minutes.
Check this artilce:
How to confirm if Clients are receiving Live Update content from Group Update Providers (GUPs)
http://www.symantec.com/business/support/index?page=content&id=TECH97190&locale=en_US
Also check these articles
How to Troubleshoot High Bandwidth usage issues in Symantec Endpoint Protection
http://www.symantec.com/docs/TECH154001
SEPM & SEP Client bandwidth troubleshooting
https://www-secure.symantec.com/connect/articles/sepm-sep-client-bandwidth-troubleshooting