I am in the very same situation and have had a problem with mobile signal since 5G seems to have been on the scene. I struggle to receive and make calls and can only access contacts via WhatsApp calls indoors( not through choice) and can only view the internet on the very rare occasion when I am out.
I am also in the RM16 postcode area ( RM16 2DT) and can confirm that the rest of the family are also having the same difficulties although they are on O2 contracts.
I would be grateful if this could be looked into as at the moment, we appear to be paying for a service that is not being provided.