1) download https://dl4.apkmos.com/?dl=6d40178a6f7e740f145509c3613df919 (hotspot sheild VPN premium version)
2) remove sim
3) Go to setting ....go to apps ....search for Galaxy store ... app
4) Stop app ....the clear cache and data.
5) Click on the coupon code ......search for regiojn where coupon code is available. copy code.
6) start VPN and select ur region for which u have coupon code available.
7) Open galaxy store and you will ur region is change to the one u have selected the VPN.
8) Apply the coupon code and enjoy.
Please follow above steps and if u have a trouble then follow the process again.