I left Japan without paying my bills

I had been in Japan as international student for one year.
During my stay, I shared a room with my roommate. He asked if he could extend his stay for longer and like to use my internet and telephone. I was so careless.....

I left Japan in end of 2005.....
My friend just told me last month (end of 2009) that he left Japan without paying my bills!!!

He has not paid for my AU and VODAFONE (local and international calls) and my YAHOO internet, and also gas-water-electric!

He just simply wrote to me like that! I am shocked!!!
What can I do or to who I should contact to clear my outstanding bill?

I have no plan to go back to Japan yet, but sure I will like to visit there in future.

Will it be any problem for my tourist visa application?
Will I be able to enter Japan as tourist?
Will I be in black list?

Thanks for every comments.

What can I do or to who I should contact to clear my outstanding bill?

You should contact the companies whose bills you neglected to pay.

Vodafone ceased its business activities in Japan in the meantime. Possibly because of the losses incurred by your unpaid bills...

The other companies are still existing, and you would help fight the stereotype of the untrustworthy foreign resident if you were to make an effort to settle your bills.

(un)fortonately for you, Softbank KK took over Vodafone's operations and is still running, so you might want to contact them as well abotu your outstanding bills.