The current PAYG Ts&Cs say, under General on the very last page, "Unless we tell you otherwise, all of our ‘unlimited’ offers are truly unlimited and must be used for your personal non-commercial use" - which isn't a very helpful wording.
Unlike some of the other networks, Vodafone doesn't give any indication of what is or isn't deemed to be covered by "personal non-commercial use", but clearly all networks have automated monitoring in place to prevent the sort of abuse described by @AnnS, and I can only think that @rich5563's pattern of use has triggered the monitors for some reason.
At least one of the other networks actually specifies a limit on the number of separate contacts over the course of a month which can be accepted as personal non-commercial use - not many of us have 500+ friends and relations. That sort of approach seems very useful, as it means everyone knows where they stand. Interestingly, it might also cast some light on the "I'm in the middle of organising my wedding" type of problems I've seen reported occasionally in this context.
Contacting Live Chat should sort the problem, and may also give rich5563 some insight into what may have triggered the monitors, and perhaps avoid a repetition of this problem in future months.
