2TB ssd harddrive for 2015 MBP 15”

I would check everymac.com for upgrade possibilities for which of the various 2015 MacBook Pro models you have.

It may be possible to upgrade but this is apparently not something considered standard by Apple as a post-purchase thing. They may not be willing to do it and if you do it yourself or have a third party do it then Apple may refuse to ever look at your computer again, even if there's a recall for some reason.

The model to which you refer uses PCIe SSDs. They are proprietary so you will need to see if the one you have will fit in the available slot. If what you have is a 2.5" SATA form factor then it will not work. As for the disk controller,ds I do not know if it will recognize that large of an SSD given that when the computer was made there was no such animal.