we have a CICS 4x8 can you get key codes to upgrade to a 4x16 or is this done only by changing out the flash memory card .

I have a older version of c/p 150 and it works fine on a old 128 (8x24) I have in my shop.. but have a cust. whose nam is failing so was wondering if I got them a cp 150 to work with their older system until they upgrade to a mics ,I understand Nortel blocked the newer version of c/p working with the older KSU's . Is this correct and can it be undone? tks.