Is the ssd upgradeable on MacBook Pro 15" with Touch Bar

The SSD is soldered to the motherboard. You will have to return it and get the one you wish or do some very risky de-soldering which has a 1% success rate.

"Get buyers remorse. Take it back and get the model you need or you may be stuck with it for a couple of years until OWC comes up with a replacement. See their blog here:

http://blog.macsales.com/38440-ssd-in-la..."