No. The CRTC does not have the power to block credit card transactions.
The CRTC has the authority to pull the TV station licenses, pull cable TV licenses, and in general, block or prevent any over-the-air broadcast activity. They also have the authority over any telecommunications providers in canada (over-the-wire or over-the-air.)
Netflix does not fall within any of the CRTC's typical mandates, other than the one that encourages Canadian content. However, the CRTC can only influence Canadian content via its other powers over broadcasters and cable companies.
A full list of the relevant statutes and regulations is at: http://www.crtc.gc.ca/eng/statutes-lois.htm.