There's a huge convenience benefit. There is also a potential financial benefit to the extent that there are different cost structures between mobile and fixed-lines networks - in principle it can be passed on to the customer.

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One of the driving forces behind FMC is that the phone itself will automatically switch to the most appropriate network. This will depend on the location of the user and their requirements, be it the cheapest, quickest, securest, or highest-quality service available.

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