Not sure about other carriers but NTT  DoCoMo only allow a certain few 
handset types. I think they have the "credit left" type firmware shit inside

"Brett Robson" <deep_m_m@hotmail.com> wrote in message 
news:cp5n5q$6t6$1@nnrp.gol.com...
>
>
> pokopoko3k wrote:
>> i'll be in japan for a month (actually about 5 weeks or so) and it sure
>> would be handy to have a keitai for this time... the prepaid ones sound
>> nice but i'd love to avoid shelling out the inital 5000-10000 for the
>> phone itself (especially considering what my pathetic dollars buy right
>> now).
>>
>> i heard once about buying a used keitai and then just getting a card
>> for it.  anyone know about this option?  or anyone have an old keitai
>> they'd like to sell/rent to me?
>>
>> i've got another question that will make you pity me further, i'll put
>> it in another post...
>>
>
> Japanese phones don't have SIM cards like in most countries. I don't know 
> if you can just turn any old phone into a prepaid version, I suspect you 
> can't.
>