You can remove PayPal from Google Pay on the PayPal website or the Google Pay app.

• On the PayPal website, tap the Settings gear icon, select the Payments menu and select Pre-approved payments. Go to "Google, Inc. " from the left navigation bar and click Cancel.
• In the Google Pay app, tap on the PayPal card, at the bottom of the details screen, select the menu in the right corner (...) and click Remove payment method.

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