BT. That means exclusive service to BT customers. That is, customers who pay their money directly to BT - we're just about all BT customers because BT owns nearly all of the infrastructure and takes a big slice of all the revenue.
But BT customer service is appallingly bad, and their executives call anyone racists if they talk about not being able to understand what their grade Z Indian call centres are saying. (Whilst claiming they are grade A centres, even though with those you usually have to make an effort to even notice).