Selling My Debt

help
i have been paying nco financial in canada and i am disputing the amount they say i owe.i have been in contact with consumer protection in new brunswick canada and nco about my file.
i ask nco for accounting info.on this account and they sent me payment history of some sort.shortly after i was talking to nco collection agency and told them i wanted told info.on this account,next thing i know cbv collections is calling me.i call nco and they told me the original creditor wells fargo sold the account and he didnt know to who.cbv never sent anything to me stating they now own the account, the real way i found out that cbv now has this account was throuht the credit bureau.do i have a right to send them a letter of debt validation and is there any repercussions in me doing this and why did nco collections or wells fargo sell my account when they knew i was going to ask for valiadtion
derrick