If you are looking to get a refund for a purchase made on your iOS device, you need to contact Apple. They will be the ones handling this process for you.
In most cases, you will have to contact the iTunes department directly. iTunes don't have a direct phone line and their support works only through email and chat. If you want an Apple advisor to guide you through the process over the phone, you can find the appropriate number to dial here! Make sure you select the correct country at the bottom right of the page so you can get the correct contact information.
If you prefer to contact iTunes directly, you'll have to go here. Again, make sure you select the correct country at the top of this page.
Once you get the page open, follow these steps:
1. Select iTunes from the produt selection bar
2. On the menu that comes up to the right, select iTunes Store
3. On the page that follows, select Purchases, Billing and Redemption
4. After you select this, choose the option that best suits you as shown as an example on the picture below
5. Once you hit Continue you will be given some options. Please choose either the Chat or Email option in order to speak to an iTunes advisor. Fill in any forms you are asked to with as many details possible, including the Order Numbers associated to your purchases (learn how to find those Order Numbers here).
They should assist you from there on :)