Amongst other things the cost of calls to 08 numbers increase.

See: http://www.vodafone.co.uk/campaigns/price-changes/pricechangesjuly14/pricingchanges1/index.htm?cid=vnty-vod-auto/azjujthumnthqs1&dfacid=1&cid=aff-aw-default-78888

Vodafone will apparently estimate how much bills will rise based on a three month profile of each customer's bill.

It will then warn customers if their bills are to rise above 10% and give them the right to leave the contract without charge.

But the company says if they wish to do so, they must write to Vodafone before prices are raised on 28 June.