I believe you're looking for

http://www.dell.com/downloads/global/products/pwcnt/en/app_note_14.pdf

or the "management access-list" command from

https://supportapj.dell.com/support/edocs/network/54XX/en/CLI/HTML/manageme.htm

The following should permit https, snmp and ssh from 192.168.2.0/24, and no telnet from anywhere.

management access-list no-telnet-please
permit ip-source 192.168.2.0 mask 255.255.255.0 service https
permit ip-source 192.168.2.0 mask 255.255.255.0 service snmp
permit ip-source 192.168.2.0 mask 255.255.255.0 service ssh
deny service telnet
deny service https
deny service snmp
deny service ssh
exit
management access-class no-telnet-please
exit

i did that and it still accepts telnet. any reason why that would be?

Got it working, thanks!