Mmm... If they called it "third-party router penalty" you wouldn't be wasting all this time with this.
Obviously they want to make extra money on top of what you pay for the internet. That comes in form of renting you a router or getting the money anyway with a fee.
The naming is wrong. It shouldn't be called "maintenance fee", but it doesn't look like there's anything you can do.
You need to have your own IDs IMHO, so that people can associate multiple accounts (ex., both Facebook and Twitter). Could you go with something simple, like a timestamp with microseconds or a timestamp plus a random number?
If you don't want to allow that, why not just to fb_{facebook_id, tw_{twitter_id}, etc.?
It's better if you don't remember which email you used to signup, as it validates it right away without you having to enter the password, so you can make multiple attempts more quickly.
It somewhat looks better because after you've entered your email they can show your profile picture.
On Chrome at least, autocomplete still works, so you don't have to enter your password manually if you have it saved. I don't know if other browsers (or even Chrome on certain websites) might get confused if username and passwords aren't together.
It makes it seem easier to login. Having to fill 1 field twice feels better than having to fill 2 fields once (in my opinion, at least).