Know who owns the refund
Refunds for purchases made through an app store are usually decided by the store. Say so plainly and link to the store's refund page instead of promising what you cannot grant.
Ask for the proof you need
For a missing item, ask for the player ID, the purchase receipt and the time of purchase. Put the list in a saved reply so every ticket starts with the same questions.
Restore what you can
If a purchase went through and the item did not arrive, restore it and apologise once. Delivering the item is a better answer than a long explanation.
Explain bans and suspensions calmly
State which rule was broken and what the player can do next. Avoid arguing about evidence in the thread; keep the wording short and consistent.
Protect minors and accidental purchases
Treat a parent writing about an accidental purchase gently. Point them to the store's parental controls and refund route, and offer help with the account.
Track what keeps breaking
Tag tickets by cause: missing item, lost progress, purchase error, ban. A weekly count shows which bug costs the most support time.