Hello.
Welcome to the Three Community.
It's disappointing to hear you're having so many issues with the connection on your phone. Given you're having the issues at so many locations, and for so long, it's usually an indicator that there's a device issue. That's not for certain of course, but it's normally the case. I'd recommend trying another phone if you have one spare, or if some one doesn't mind letting you test your SIM in their phone, this will allow you to test it out and see how the devices compare.
If you'd like to explore the network as a possible cause for the issues, you can enter the details of each area into the service Status Checker.
As for not being able to pay in stores with your phone, I have no idea why that would be. I'm assuming you're referring to using a service like Google Pay? Those payment services are designed to work completely offline. The data required is in the phone, and the terminal you're trying to pay through is the internet connected device that verifies the payment. I'd recommend reaching out to the manufacturer, or the provider of the payment service you're trying to use to learn more about that, as Mobile Payments is not a feature that relies on the mobile network.
Pete.
