Again u still need to put the right apn settings. On android apn settings depends on what device you have and what data plan you on. Put in the wrong one and they'll know and add on the tethering plan and if u have unlimited data plan it'll be gone. Custom roms make it easier but it's still trial and error.
For example on AT&T
4G LTE settings
Name: Nitro Default APN
APN: pta
Proxy: <none set>
Port: <none set>
Username: <not set>
Password: <not set>
Server: <not set>
MMSC:
http://mmsc.mobile.att.netMMS Proxy: proxy.mobile.a
tt.net
MMS Port: 80
MCC: 310
MNC: 410
Authentication type: <not set>
APN type: default,mms,supl,hipri
3G settings
Name: AT&T US
APN: wap.cingular
Proxy: wireless.cingu
lar.com
Port: 80
Username: <not set>
Password: <not set>
Server: <not set>
MMSC: <not set>
MMS Proxy: <not set>
MMS Port: <not set>
MCC: 310
MNC: 410
Authentication type: <not set>
APN type: default,supl,agps,fota,dun
4G HSPA+
Name: AT&T US HSDPA
APN: phone
Proxy: <not set>
Port: <not set>
Username: <not set>
Password: <not set>
Server: <not set>
MMSC: <not set>
MMS Proxy: <not set>
MMS Port: <not set>
MCC: 310
MNC: 410
Authentication type: <not set>
APN type: default,supl,agps,fota,dun
Tethering settings
Name: AT&T US Tether
APN: broadband
Proxy: wireless.cingu
lar.com
Port: 80
Username: <not set>
Password: <not set>
Server: <not set>
MMSC: <not set>
MMS Proxy: <not set>
MMS Port: <not set>
MCC: 310
MNC: 410
Authentication type: <not set>
APN type: tether
MMS Settings
Name: AT&T US MMS
APN: wap.cingular
Proxy: wireless.cingu
lar.com
Port: 80
Username: <not set>
Password: <not set>
Server: <not set>
MMSC:
http://mmsc.cingular.comMMS Proxy: wireless.cingu
lar.com
MMS Port: 80
MCC: 310
MNC: 410
Authentication type: <not set>
APN type: mms
Your SIM card also has to be provisioned for it meaning if you have a 3G device u can't pop your SIM card in a 4G LTE device and expect the 4G LTE settings to work. And you never never never want to use the official tethering apn or you get caught. U can also cheat the throttling by switching apn settings after u get throttled. It's been nice when I sometimes tether from my iPhone 5's 4G LTE speeds. But I rarely do it because I don't want to risk my unlimited data that's getting amazing speeds. Used 44 GB last night lol.