Yeah, or just tell them to get lost.
http://www.bennettjones.com/Images/Guides/update687.pdf
For further reference, in Alberta, the existence of preagreed limitation periods has been a bit of a sticky and confusing point even among lawyers. Ontario ironed it out a long time ago but a statuory ammendment to the Alberta Limitations Act prohibiting such extensions, while it was drawn up in 2003, didn't come into force until April 1, 2006 as can be seen from the link above.
Obviously, our blogger's contract with the fertility clinic occurred prior to 2006, and so that's why I said he should try and get a copy of the original invoice just to be safe.
However, so as not to go into a lot of unnecessary detail, create confusion and because it was a relatively small amount, I simply advised the blogger to tell the collection agency to buzz off or settle for a small percentage if he chose to do so for moral reasons.
Ray