Well, every carrier charges you for the mobile hotspot option in some way. On AT&T, I pay for the 5 gig a month data plan so my Galaxy S3 can be one, and, believe you me, I do not need anything like 5 gigs, since I have so much access to wifi (home and office). But I pony up so I can connect all my devices if I am out in the netherworld.
I installed Open Garden today, it works. Had trouble receiving email, but was able to view websites.