Poor service

[Smithereens41]

My service is really poor. Signal is appalling and data is terrible. This is the second simcard to do this. 1st one I lost ten pounds on and now this one. I'm 20 ft away from a cell tower so what's going on. Tech support say signal in my area is 5g. Rubbish I won't keep paying for crap service mind. Been with o2 now for over ten years. A change might be in order

[Enlli]

If you are PAYG then you can't access 5G and you need 3G to make voice calls

All we can do here is point you to these guides

Guide: Is the network down for me or everyone? 

Guide: How can I sort out my network issues? 

[Oxonian]

It is mentioned in the guides provided to you @Smithereens41, but I would suggest that you take a look at this app :-

My Network App - Find Out More About Your Network Coverage | Apps | O2

https://www.o2.co.uk/apps/my-network

Understand your network coverage

With the My Network app you can keep an eye on your coverage, wherever you are. Download the app and you’ll be able to:

- check the status of our network in your area – you don’t even need to enter your postcode
- test your network speeds
- report any issues with your service.

It’s simple to use and means that you can check the network without having to visit the main site or even enter a postcode.