You can't change the speed.
It's max 3MB and your traffic always takes priority.
You can't make any changes to BTWifi-Fon but you can opt out of it if you want.
If you do opt out you will not be able to use BTWifi hotspots when out and about.
See link about opting out.
Thanks - does the visitor's usage add to the host's usage, such that the host's monthly allowance might be exceeded?
any usage on BTWIFI/FON is not added to the home data usage