I think I finally got 'The message'.........

"From Vodafone: To let you know you're nearly at the end of your monthly data allowance of 500MB. If you need to use additional data there will be a charge of £5 incVAT per 500MB , however we won't start charging until 1 October 2010. To stop these alerts, text STOP to 40506 Sent AUG 20 @22:32 UK"

Time to trawl back through the thread to find where it is I need to send the letter/email. Probably not worth the effort ringing them as no doubt I will just get the run-around.

Does anyone think it makes any difference if it says they won't charge until October?