Non retina you can upgrade the RAM yourself. Officially Apple only supports 16gb in those but I have done a non retina RAM upgrade to 32gb myself.
It's the late 2013 model i5 with SSD and Retina screen.Depends on your model. If it's the plain Macbook Pro without the Retina and SSD, you should be able to up it to 16GB. If it's a Retina, then you're SOL.
What modules did you use?
2x16gb modules. Only place I could get them in a store without too much hassle was Incredible Connection strange enough. They were like R2400 each. Kingston 1333mhz.
Are you sure? R2400 is roughly what 2x8GB DDR3 SODIMMs go for. Kingston doesn't list 16GB modules. Google doesn't know about them either. I've only found one manufacturer that lists 16GB SODIMMs, and you can't buy them anywhere (don't seem to be in production yet).