While you can't buy them with cash, you can use (the common in-game currency) to effectively purchase Phoenix Credits:
: Every Basic Sealed Cache contains one random gear item and a small amount of Phoenix Credits (typically between 13–24 credits ). the division buy phoenix credits
Once you've reached Level 30, you can spend these credits at specific endgame vendors: While you can't buy them with cash, you
: You can sell the gear items you don't need back to the vendor for more standard credits, then use those to buy more caches to further increase your Phoenix Credit total. Where to Spend Phoenix Credits 000 credits each.
: Visit standard weapon or gear vendors at the Base of Operations or safehouses. You can buy these caches for roughly 400,000 credits each.