A a Canadian citizen, you can not be refused entry to Canada.
Failing to respond to a civil lawsuit (which debt collections are) may result in a default judgment against you, but it is not a crime. Someone who is falsifying service is probably committing perjury, which
is a crime. Reputable process servers won't do this.
As a dual citizen of the U.S. and Canada, you cannot be refused entry to, or deported from, either country.