I just got a call trying to sell me BT Infinity.
Clearly banking on the BT name, the operator said "as you may have noticed, we've just finished doing a lot of upgrade work in your area" - though I don't suppose many people will realise BT Openreach is a separate part of the BT business that is required to deal with third parties on the same terms as BT Retail.
I said, truthfully, that I'd placed my upgrade order with a business-grade provider (i.e. Zen) two days ago. I was asked why I'd gone with Zen, so I stated I was a previous customer. Getting desperate, the operator claimed that BT Infinity could give me everything I needed. "Routed /28?" "Thanks for your time".