I had an interesting chat when my contract ended with Voda, i made a few noises that i might jump ship and the guy let slip that they like all the other companys "offer" a loyalty bonus to stay.
I got £90 and got to pick form the latest phones
Obviously there is a limit and if you go for a really posh phone then the bonus goes towards to cost of it
Me being a tight wad took the Samsung soul and the dosh