The only thing the merchant controls is the capabilities of their card reader. Any or all of the 8 CVM's can be allowed by the card including no verification at all. It sends a list of what it will accept. Often, a chip and PIN card will allow backup verification methods including signature. The card issuer controls the list because they are the ones at risk but they also want to minimize inconvenience to their customers, hence the multiple options. When that approval code comes through the merchant is clean.

Every single car issuer determines what they will accept for verification and every single terminal maker bakes in different capabilities (within the limits of the specifications) so it is not at all surprising that we are running into lots of potential issues especially in SXM where the merchants were used to swipe and signature (Americans) and chip and PIN (Europeans) until last month when they started to get hit with chip and signature. It isn't any better in the U.S. where merchants are all over the map in support and are mostly still doing swipe and signature.

My guess is that you will see support for the chip functionality first in the jewelry and other high end shops since the merchants are now liable for fraud loss if they don't use the chip technology (at least they are in the U.S.).