UK Problem - Mobile Provider on Base Station

The base station has selected 3uk which has a very weak signal in our area. O2 and Vodafone are significantly better and EE is unusable. Can I change this setting so the base station uses O2 as it is by far the strongest signal in our area. Ring US support staff unfortunately haven’t got a clue what this means for UK customers (which is frustrating) and their ‘support bot’ clearly doesn’t recognise the issue. Thanks