new dell inspiron 15 gaming series hard disks

Hi,i found this new laptop amazing and i wanted to buy it on the dell italy ecommerce.

This laptop has a double hard disk system, hdd 1tb 5400 rpm and ssd 128 gb. I just wanted to replace the hdd 1tb because it's old and get a 512 gb ssd.I couldn't find some specs so i asked twice to che assistance chat,but they seems a bit counfused about my request.

The first one told me that the hdd and ssd are welded to the motherboard and not replaceable.

The second one told me that the 128 ssd can be upgraded to 256 but the hdd 5400 is the only compatible.

Can you please help me? i like this laptop and i want to buy it but i don't want an hard disk whith a 10 years old technology.

Thank you