Here is one simple method to getting Premium Currency LEGALLY for free on SAS: Zombie Assault 4 with ZERO chances of getting banned.
1) Use CashForApps, FreeMyApps or AppBounty to get points when you download free apps.
2) When you have enough points, they will reward you with a gift card for Google Play or iTunes
3) Redeem these giftcards and use it to buy Premium Currency in SAS: Zombie Assault 4 – no hacks, no cheats, this is a legitimate method to get Premium Currency for free in SAS: Zombie Assault 4.
How to Redeem these Gift Cards if you're NOT in USA.
Lets assume you earned a US Dollar gift card and need to spend this gift card.
1) If you play on Android, you'll change the currency of your Google Wallet to US dollars.
To do so, you need to change your Google Wallet Home Address. Find a Valid USA address to use and change your current Google Wallet home address. Item prices will now be reflected in US dollars.
2) If you play on iOS, you'll need to change your store to the USA iTunes store. Go inside the AppStore App and then click on “View AppleID”. There you are able to modify your home address to USA.