[levymetal]

It's the same as all other companies. "Switch to our Halifax, and get £100 free. Offer only available to new customers". It's rare to see a company that rewards existing customers instead of disregarding them and focusing on the new ones.

[Osmium]

Pleasingly some mobile networks in the UK are doing this, but that's only because they have an incentive to retain customers. I don't know of a good competitor to Skype. Google Voice, perhaps, except it lacks subscriptions and a nice native iOS app (to my knowledge).