[andy]

On the Isle of Man SIMs the tariffs (including some free roaming countries) are set by the reseller, but most have the 30 then 6 second billing units, (I thought all of them until I read the OP).

Talking of Globalsim, there is and was a German operation with this name well before the UK one started using it and confusing the issue; the person behind the UK one also has another trading name borrowed from a UK company so I'm not that impressed by seeing ™ on his Globalsim branding

The renewal conditions of the CallKey brands also seem to vary; to begin with the notes in the leaflet with the SIM mentioned a possible annual fee, but a couple of dealers didn't yet know at that time. Now some specify either an annual fee or top-up every so often.

On my particular one (bought from 0044 but now transferred to Simazing - by them) I was told that there is no annual fee, but a reactivation fee if it isn't used for 6 months; the minimum top-up on this is $50.

I think the variation of renewal and top-up conditions between the various resellers could become as significant as the initial credit or the call tariff. £20 or £25 starting credit included might not be as attractive if it needs $40 or £40 a year in top-ups when most outgoing call tariffs are now near to or actually higher than using an O2 UK SIM or Vodafone Passport

And like any of these global SIMs it can be used with independent callback, so I will probably avoid topping up unless (unforeseen at the moment) I go to a country with charged incoming calls; the balance has been 18c since May. (I've never topped up my Riiing SIM in two years either)

As for the additional charge mrbarlow mentions, this is the supplement while using it for conference calls, and applies on all of the brands