Buy More Disks for Dell Unity 300

Dears, We have unity 300 Storage that have only 11 Disks installed and and it works fine but I need to increase the size of storage. 

Since it have about 13 empty place to add more disks, I have contact a local reseller partner to buy more disks but he response me that this no longer available an say that  "Expansion for all Unity xOO/x50F models are no longer as of the September 30, 2022 End of Expansion date"

so is it right that I can't buy more disks to install it in the storage.