Go into Settings|Mobile Data and see if there's an option to Get Settings from Provider. If there is, tap on it and it'll donwload the correct access point, install it and delete all others. Also look at Access Point Names and check that Vodafone Contract (or PAYG if you're on that) WAP is there and has a green dot beside it.
If none of those applies, text WEB to 40127. The response will imply you'll get another text, but settings tend to install silently these days, so don't worry if nothing appears to happen. After a bit, check back for the WAP APN.
If the APN is there, the chances are that MMS isn't provisioned on your account. In that case, talk to Live Chat (Contact Us at the botom of thr page) and ask them to do it for you.
