You're a Bunch of Factors

My son is home for Xmas/New Year he is always downloading heaps, I get an email just B4 christmas advising that I have 20% of my download limit left and when that is reached I will throttled to 64K, the next day another email tell me I have maxed out.

Both my son and I are with TPG, he also brought his wireless modem /router with him, he suggested we try replacing my modem with his to see if it works, sure enough we are now back to full speed using his account.

You learn something everyday

Yeh GD thats always been possible, however if you read your T&C's it says the service is to be used at one address only.

It's pretty unlikely they'll pick up on it, but if they do they will cancel both services.

Wasn't so much changing the modem that did it, it was the username and password.
Could change yours to be his details and it would be the same.

Also - this wouldn't have worked on some ISPs in days gone by - they have the user accounts mapped to an exchange/port.