I have an old running contract with Vodaphone. I get 200 mins with stop the clock and 50 texts a month for £15 as well as getting a top phone for free.
I had this for a few years and this will probably only help people in a similar situation.
I have started texting more so I thought I would call Voda and see if I could add some more texts to my monthly bill and pay the extra (without extending my contract).
The girl I spoke to gave me an extra 100 minutes and unlimited texts (still with stop the clock) at no extra cost and without extending my contract.