This issue most likely has nothing to do with your implementation, especially if you use revenue management platforms like RevenueCat or Adapty. It's more likely the behavior of Android users using prepaid cards with zero-balanced or cash payment as their payment methods, and is a well-known thing called 'trial period abuse'. You can set a longer grace period in hope for them to top up the card (probably to pay for in-game items), but they will also gain longer access to your trial subscription. So if you have the servicing cost during subscription, it's better to write off these pending charges and focus on users who actually pay.