Manage refund of non consumable

Hello,
for the first time I am trying the integration with revenuecat for one of my apps (flutter) present on both stores.
The goal is to remove advertising with one purchase only (non-consumable).
The purchase works, the recovery after an uninstall works, but I don't understand how to manage
a refund:  If the anonymous customer asks for a refund (or if I refund him), the purchase is always valid and isPro is always true.

PurchaserInfo restoredInfo =
                  await Purchases.restoreTransactions();
              if (restoredInfo.entitlements.all['all_features'] != null) {
                isPro = restoredInfo.entitlements.all["all_features"].isActive;

What am I doing wrong ?
Thanks in advance.
Enrico