Unlocked iPhone 1st gen with t-mobile w/o contract.

[dranfi]

Hello,
I'm a French student in the US and I'll have to leave in june 2009. I've got an unlocked 1st gen iPhone. I'd like to use it with a great plan (not expensive, unlimited data or at least 500 Mbytes/months and at least 200 SMS+months). Now I'm using an AT&T Pay as you Go (because I wanted to try AT&T, since it is the official iPhone carrier and because for any others plans they require a credit card which I didn't have, but now I've got a wells fargo credit card; btw, is it a good/safe bank?). But I'm very unhappy of my AT&T experience : 1stly these dailly fees for nothing which make me refill my account very often, secondly I asked for 200 sms and their expiration date is not the account expiration but only 1 month and last but not least, I call AT&T to ask them to remove any data access from my phone, they say "ok", I insisted to be sure and make sure I understood well. Then I had the surprise to have fees like 16$, 6$ of GPRS, then I call again AT&T and they told me that they cannot cancel Internet access from my phone! I'm very happy!
To sum up what I paid:
total payed : $55
Voice : $14.00
"data" : $25.42 for nothing (since the iPhone automatically connect itself to refresh mails, stocks, weather...; hopefully I found bossprefs to turn EDGE off.
SMS : $5 (package of 200 SMS which I only used 50 :p)
dailly fees : $18
"gift" : $10 they "gave" $10 credit, which is not even they dailly fees!
And I had to add $15 if I want to have some credit until I change company.

So I want your help to find a plan without contract, SMS plan (200/months should be find), unlimited (or a lo of MB) and how to configure the phone (cellular network parameters like APN, Username and password for edge navigating). I'd like to know exactly what you have to pay (incoming/ outcoming calls, incomming/outcomming SMS, time is rounded to the nearest minute or up, what happen if I use more minutes/SMS/Bytes than the plan, if the voicemail is free and how I can contact my voicemail). I'd like to transfer my AT&T number, is it free, how can I do it? What can I do with the different data plans (i.e. : web browsing, receiving mails (pop3/imap), tethering, VOIP) and if I need a special configuration for the plans (ie using a kind of proxy and modifying some configurations files on the iPhone which are normally not modifiable)? And what I need to bring in the store (passport, actual AT&T sim, at&t recipe for the number, credit card and phone; all of them? or I forgot something? )? And what should I say, should I say it's for an iPhone or should I take another phone (I got an unlocked samsung zv10 since in France unlocking is free after 6 months of contract, by law)?

Thank you for your help.