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I "bought" my S7 when new (out one month) on a £24 month contract (unlimited minutes, unlimited texts, 6GB data)

Is 6GB not "decent"? I don't tend to get near unless I have turned wifi off "by accident" (usually as a means to stop it trying to connect to use a weak network when the connection is poor, e.g. after leaving the house, getting into the car, then trying to put in an address into the sat-nav app.) and then start watching lots of YouTube, forgetting to turn it back on again.