Router for mobile wireless USB modem

diamonds

looking at a broadband solution for someone but they need a router that takes usb from a mobile network usb modem instead of an adsl input, I know Linksys do a data card router but seems in UK you can only obtain this on Vodafone via a data card & router is locked to Vodafone

they want to have a landline ( read lifeline ) so i thinks VOIP via router for incoming/outgoing calls is only option as a landline is not a possibility in such remote area but served well on 3.5G by T-mobile & 3 , cost is imperative as its for a elderly person and a mobile running costs, topping up & them learning how to use a mobile phone is beyond the persons means, a telephone is a telephone to them so voip via router via a " normal " phone seems to be the only way but im unsure if such a router exists other than the Vodafone £25 data card per month option, then thers the £100 for the Vodafone/linksys router ontop