You don't mention is you are on PAYG or monthly contract @Kiwiphil but it shouldn't make any difference, there are no roaming charges for the Isle of Man. Would recommend doing a manual roam from your connection settings and select one of the Isle of Man networks but it looks like you have already tried this.
Unless you have already tried, make sure you are dropping the first 0 and using +44 for texting and calling back to the UK.
Other than that, you will need your account checked, you can contact Vodafone from the Isle of Man using +44 7836 191 191 from the Isle of Man using any other phone, although free from a Vodafone mobile. Alternatively, speak to the Social Team but difficult when you need a quick answer here: Contact Us
