Next update
Some many problems in 6 not working google pay and sometimes I am veryed to tha phone I am very poor family so i am not buy tha iPhone no money
iPhone 13
Please watch my GIF made on iPhone 6 where a transaction of Rs 500 was made using Google Pay.
This says that you are referring to UPI pay and not Google Pay
See the pic below which clearly states you need iPhone 7 for UPI.
Every app has its own boundaries. Please contact the app developer --> How to contact an app developer - Apple Support