HFC - HSBC Group ripoff dishonest fraudulent overbilling Livermore California

In Dec. 2005,I received an offer of an unsecured simple interest installment loan of $7,000 from HFC which I accepted. I paid this loan payment early each month. After one year I had paid back $2,652.

In Feb. 2006 I decided to pay up the loan so I sent in the amount showing on my statement balance which was $6,133.

In March 2006 I received another bill from them for $285. I called to find out what this was all about because I had just paid my balance in full and I hadn't had any missed payments or late charges. I thought for sure it was a mistake.

Well, the $285 was a mistake. Just three weeks after I had paid up my balance they said that I owed another $453 by March 31 if I wanted to consider my loan paid up.
When I asked why if I paid up the balance that was on my statement did I now owe another $453. I was told that I was being charged simple interest.

Simple Interest on what ????? My balance should have been zero. I have very good credit and I had already paid an enormous amt. of interest in one year.
How does a period of three weeks accumulate a balance of $453 from a paid up account.

Christen
Livermore, California
U.S.A.