Configuring Cisco IP phone with 2820n

I have a Cisco IP phone which I'm trying to configure with my Draytek 2820n router.<br/>
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The router is running DHCP. I have entered the IP address supplied by the company who will be routing calls to me within DHCP, and binded it to the MAC address of the phone. <br/>
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It was working for a few days until my IP address changed. My ISP issued me with a static IP, which I supplied to the company routing calls. Since then, there has been a constant "Configuring IP" message on the Cisco screen.<br/>
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Any ideas?