I went with Asda Mobile about 8 months ago and went to but the cheapest Nokia they had on offer at £9.99 but they had sold out at Preston when we went.
The tarriff at the time, which is what attracted me, was 16p/min for 1st 3 mins then 8p for rest every 24 hours and texts were 8p each for 1st 3 then 4p each in the same period.
The Duty Manager at Asda was at the counter when I went and let me have the next model up, the Nokia 2340 for the £9.99.
Up to last month, every time you topped up at Asda you got an extra 10% value added. Then when they texted that they were ending the 10% offer they also informed us about the new tarriffs which are great value.
Asda operate on the Vodaphone network and I have never had a problem with that.
dave