As alluded to previously, while there might not be a true cap, there is likely a level at which AT&T will begin to look. It's hard, for example, to download even 1GB/month with typical iPhone use. Someone who was downloading 5GB/month would certainly be abusing the service, as that translates to (if I'm doing the math correctly) about 120KB/minute, 24/7. Nobody does that. So I'm sure AT&T could easily set up a threshold and snag people who are over a reasonable limit and then look further. I don't know what that limit might be, but I'd personally think that even 1GB/month would look suspicious, as I doubt that even 1% of all iPhone users even approach close to 1GB/month.
Obviously, they could also just inspect the data itself, and something as trivial as the browser descriptor could give away the fact that you're not surfing from your iPhone.
However, as a guess - and only as a guess - if you use tethering but keep your use to a minimum, you should be OK. But I'd use it very little.
Obviously, they could also just inspect the data itself, and something as trivial as the browser descriptor could give away the fact that you're not surfing from your iPhone.
However, as a guess - and only as a guess - if you use tethering but keep your use to a minimum, you should be OK. But I'd use it very little.
