As far as I know Telstra don't lock there Routers but it's probably Band Selected through their Firmware.
Is the Router Branded, ie has Telstra logo on the Router.
Telstra also do not use EE's 800mhz Band so again that may not be available within the Lookup table within the Firmware, where abouts are you within UK, Main Town or Rural.
Did you change the APN Settings within the Router for EE requirements.
