SKS Associates Northern Leasing Sks Ass. stole money from my checking account 8 yrs later Internet

On April 4. 2011 a company called SKS Ass. debited illegally from my business checking account $100.00 for which I new nothing about. When I called the phone# 866-286-8841 from the transaction I was asked if I had a Lease for any equipment with a company called Northern Leasing. Back in 2000-2003 I used a credit card terminal from them for my business. I have not used Northern Leasing since 2003. I wss told they did an audit and found that I owed $100.00 for administrative costs and Sks (a third party) debited it from my checking account. I did not authorize this transaction nor ever hear of SKS Ass. My bank allowed the transaction to go through. I'm not responsible for these so called fees nor do they have any proof. How could a company bill me for something I haven't used them in 8 years? They faxed me a letter on September 15 2011 saying that I was notified of this. I never received this letter. I asked to speak to a manager there and I do not get put through. I contacted my bank to deposit the money back to my account, that they should have never agreed to this without my authorization. I'm the only one listed on this account. The only one that signs my checks. I have no business with this company or Northern Leasing and they cannot prove I owe them any money.  I want my money back and I want it now. Someone is responsible for this happening and they need to PAY!