There is nothing inherently wrong with "only" a certain number of bars, what matters is the service you are getting from the network. You mention that calls are "virtually impossible" to make and receive, but can you explain more about the specific issue? What is happening when you try to make or receive a call?
And as per the reply from Linzi already, can you more specific about what "everything" is that you've tried, because we don't know.
North Wales is also quite a large area - is there a particular location within North Wales that's proving problematic? And how long has it been a problem?
