Book Antiqua[SIZE=1]1[/SIZE]blue

My question is probably a common knowledge question, however not for me. About 2 years ago an ex-girlfriend (of Course) and I went into a jewelry store that my ex-girlfriends best friends mom worked. We found a ring of course that total was around $1200.00. I put 25% down. At that time her best friends mom hand wrote, on a piece of paper, 12 months sac and I signed. This was about two years ago. This last week I get in the mail a notice from a collection agency stating that I owe said Jewelers $6,000.00. Needless to say I am furious. The "mom" has not returned my calls. So I am in the middle of writing the collection agency back wanting proof.
So my question is this. should, could I write anything in this letter to make me not have to deal with this ever again? If it does go any further, will I actually have to seek legal council? Please help, I don't want to make a mistake here.

mr.yet

Writing to them demanding verfication of the alleged debt, have them provide you a certified true copy of the original contract. look up the code on the web for debts collectors. they are available.
Always do everything in writing only, no phones call. build a paper trail.

mr.yet