BT Retail do not provide or maintain the external network. This is done by Openreach (A BT Group Business) who work for all Service Providers apart from Virgin Media. BT Retail do not get any special treatment.
Its possible that there was a faulty port or tie cable pair when Openreach initially tried to change it over, so they just put it back through again. It would have failed the commissioning test anyway, so it should still be in hand with Openreach to sort it out.
When you get the chance, please post the results from the home hub.