Help-Advice needed

Hi:

I hope someone can answer this.  First of all, my student loans have NEVER shown up on my credit report.  I have been out of school since 2001 and paid my two provincial loans in full but never paid my federal loan through Scotia Bank.  It was 10.000$.

After not paying the Scotia bank for a few years, they sent it to a collection agency.  At first I started paying it and at one point was paying 400$ a month and it was down to 5500$.  Then I got a letter saying I owed 11,000 now. I said what about my payments, they said interest bla bla bla.  So I stopped paying.  Over the years I wouldn't hear anything from them, then it would pop up on some new collection agency report and they would call me, I wouldn't return calls.  Over the years, maybe 5 or 6 diff collection agencies and this was NEVER on my credit report.  I have a mortgage and decent credit.  Oh by the way, after I had paid the collection agency down to 5500 and then they came back with the 11,000$ thing, I contacted Scotia bank and said I will pay you, but never again a collection agency.  They responded saying I no longer can pay them because I don't owe them any money, I owe the credit agency. So anyways I stopped paying alltogether, it passed through several agencies, never on my credit report and it's been ten years now.  Today I get a new letter from new collection agency saying I owe 15,000$ for scotia student loan.  If it's not on my credit report, should I care?  If it had been on my report, it would have expired years ago.  This is why I'm assuming they don't put it on there.  Question is, if it's not on my report, what do I care? Should I keep silent or tell them to put it on my report and let it expire?  Say what you want, but I'm not paying it back.  And certainly not 15k on what was 5k.  I am in New-Brunswick.