tethering internet connectivity from iPhone

Connect you iPhone to your laptop
Disable Wifi on the laptop and also unplug Ethernet cable from the laptop.

Take iPhone, go to Settings --> then go to Wifi, Turn Off Wifi.
go to Settings --> the General --> then go to Cellular --> then Turn ON 'Cellular Data' and Turn ON 'Enable 3G'

go to Settings --> then 'Personal hotspot' --> then Turn ON 'Personal hotspot', select 'connect via USB'

Within 5 secs, you should be able to browse internet from your laptop.

No need to change any internet settings in laptop