Hi, how can i stop automatic purchasing from ITunes on my iphone 5s ?

See if any of the following articles can help:

• View, change, or cancel your subscriptions - Apple Support
• Get help with an item purchased from the App Store, iTunes Store, or iBooks Store - Apple Support

From Manage your iTunes Store and App Store password preferences - Apple Support

1. Tap Settings > [your name] > iTunes & App Store.
2. Tap Password Settings. If you have Touch ID or Face ID turned on for purchases, you won't see this menu.
   
3. Under Purchases and In-App Purchases, tap the setting that you want.
   
4. Under Free Downloads, tap Require Password to turn the setting on or off.
5. When asked, enter your password. Then tap OK.

Hope this helps,

Donni