I know I'm going to come across as a complete muppet here...

I moved house a few months ago, and the new phone line was down for a few days. I bought a Vodem stick on a prepay plan. My landline was reconnected quicker than expected, and I ended up using about 100mb of the 2GB it came with.

Anyway, I have no further use for the Vodem now, and I thought I'd sell it, but now the plan is confusing me. The 2GB has expired and I thought that it would be like a prepay phone sim; you just cannot access the network until you buy a data top up.

But when I plugged the thing in it connects up to the internet just fine. And then I read the vodafone site and it says that if I use it without pre-purchasing data it'll start charging me $1 for the first 10MB and $1 per MB after that.

My question is: what account is it charging to? When I bought the thing, I paid for it and the salesman told me that once the 2GB was gone, I'd have to buy more before I could continue using it. I don't remember linking it to any account, and I don't even have a Vodafone cell.

I see people on TM selling used prepay vodems including the sim - how does that work?