The BC limitation period is still 6 years if that's where the card was taken out.
Read Sections 1,2 and 8 in the link below below to see what applies to your case. But you are probably still on the hook until the 6 years are up.
http://www.lss.bc.ca/assets/communityWorkers/advocatesConference2008/debtAndCreditIssues.pdf
If you pay AK any money or send them a signed letter confirming ownership of the card, albeit still disputing the debt, you'll likely be restarting the limitation period. Best to keep all complaints with them to the telephone for now unless you need to settle.
Given that the debt is likely actionable; no, I definitely wouldn't ignore it.
AK is an debt buyer who diligently reports to both credit bureaus. If you pull your Equifax and TransUnion reports, you'll almost surely see your name listed under the Public Records/ Collections section of both - along with a significant dip in your credit score.