Bad Credit in Korea

I came back to Korea after being gone for 10 months. I tried to get a phone and plan but was refused. The vendor told me that my credit "was not good," and he could not issue me a phone. He was unable to give me any more details about it.

I was freaking out, I've never had a credit card and have never borrowed money in Korea.

After some thinking I believe I have pinpointed the problem. I had a phone bill and internet bill attached to my previous school and apartment that was in my name. When I left the school it wasn't on the best of terms but they assured me that they would take care of canceling my bills after the last payments were made from my deposit.

I e-mailed my previous school after the bad news from the phone place asking if they had closed the bills. After a very lengthy wait, they said they tried but couldn't (information that would have been much more helpful 10 months ago). I'm not sure if they didn't close them out of spite or if they really couldn't close the accounts, I guess it's irrelevant given the reality of my situation.

I doubt trying to explain this to someone, especially someone I'm indebted to would generate any sympathy or understanding. I would like to do the right thing and try and fix the problem. I don't want to have this impact this year's experience in Korea.

My current school has been a little less than helpful when I asked them for assistance. They seem to want to ignore the problem but I don't think it's the best course of action.

Has anyone had a similar experience?  I'm not sure of the name of the internet company, I think I was on KT for my phone. Should I contact the companies individually or is there some sort of collection or government agency I should contact?

Any help or advice would be greatly appreciated!