This will be of interest to anyone whose Three contract is about to finish its minimum term.
My term was up in November, so I phoned to cancel. One cancellation deal they are running is contract-only (i.e., no handset). This extends your number for another 12 months on the Talk & Text 200 tariff (not otherwise available as far as I've found) having 100 x-net minutes and 100 texts.
Three initially credit your account with £240 which is debited by £20 each month for 11 months. In the 12th month they debit £5.47. No cashback, no faff. They are, of course, banking on your using more than the allowance or downloading extra chargeable content.
For low-use users this is a very nice deal - it persuaded me. :) Can't wait to see what next year's deal will be. :D