One of the original UK mobile phone networks.
Initially owned by Telecom Securicor Radio Communications (if my memory serves me correctly), but later sold to BT - who were a major source of customers for the firm to start with.
Back in the ol' days, when a cellphone closely resembled a concrete block, the two networks in the UK were Cellnet and Vodafone, and neither were allowed to sell directly to the public. Instead, they had to sell via indepenent dealers, who recieved a large commission cheque for each contract they sold.
The rules are a little more relaxed now, and so BT Cellnet have their own sales department. And they are agressive; very very agressive with their sales techniques. Their current slogan is BT Cellnet - The Mobile Internet (see that? They don't acknowlege the fact that other companies provide WAP phones).
And so keen are they to sell their services, that they have a telesales department. The kind of people who phone you in the middle of your dinner. The kind of people who take a lot of persuading to shut up. The kind of people who go through every number in the phone book, rather than buy mailing lists. They won't shut up until they get certain details from you, like your name, which counts as a lead, and which they get commission for.
Have you got a phone? Is it with BT Cellnet? Oh, well, um, would you like another?