MacBook Pro (Retina, 13-inch, Early 2015)

My wife has a MacBook Pro Retina, 13inch Early 2015 with the following.

Processor - 2.7GHz dual-core Intel Core i5

Memory - 8GB of 1866MHz LPDDR3

Storage. - 128GB PCIe-based flash storage

Now the MacBook is well outs its warranty and she is now having to use alot of storage on the cloud do to the small hard drive.

My question is can they hard drive be upgraded to a 500GB SSD or even a 1TB SSD ?

When I put the MacBook details into the Crucial Site (Uk / English) it says I can upgrade but im sure I seen that this cant be done.

Please can someone point me in the correct direction of upgrading to a bigger hard drive

http://uk.crucial.com/gbr/en/ssd/series/MX500