They called me today - 31st July 2008 at 14:30ish - and I picked it up. The woman was speaking very quietly and there was a poor signal, and my phone itself bleeped when shewas about 20secs through (which was odd). She then started to ask how much I topped up each month. I said I was fine with Vodafone, and she said, "So, do you not want a better deal?". I said No.
Strangely however, she already knew that my phone was pay-as-you-go.