This happened to me so many times I sat down and concentrated on how to stop this. I would go to "Checkout" a customer, click "Review Sale" then when I hit "charge" my phone would vibrate then automatically take me to google pay. Google pay would ask me to pay the merchant with google pay. I was the merchant. I would have to tell a customer to quickly pay right after I hit the Charge button before google would stop me from charging the customer. 

                            Background: I have a Motorola One 5G phone with Android version 10. I don't know a lot about phones. I know how to use a desktop really good.  

          Finally I went into the "settings" on my phone. Then "apps and Notification" . Then clicked "disabled" and "forced stop" for google pay app. I don't use google pay. But if I did I would have to stop using it because it would keep interrupting me when checking out a customer super embarrassing.   

I would like to hear if anyone has had this issue when checking out a customer on an new Android phone. And if you use Google Pay. 

          I had an old I-phone 6 but upgraded to a new phone because I wanted to  use the square appointments app.