You shouldn't need to change ISP -they all use BT lines at the end of the day. You just need to find a way to connect your ADSL modem to the Belkin router. Does the Belkin router have an ADSL modem built-in? If so - you can probably just use that, if not then you should connect one of the output ethernet network (not US ports on the modem to the WAN port on the Belkin.

You'll probably have to experiment a bit - but you shouldn't need to buy new kit/change ISP.
Hope this helps,

Sparks
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