HUAWEI HG520b - Talktalk router

I've been given a new boxed router as above but it appears to be locked to Talktalk. Can't overwrite user name/password etc
Anyone know where I can get a firmware flash to unlock it to use for my own ISP?

Don't take this the wrong way but Why do you want to use that sad excuse for a router,? does being given it for free not give you a clue that it is gonna be a waste of time perusing & do yourself a big favor throw it in the bin

LINK

I have no idea if this is the correct firmware for that router, use at your own risk, but you can get them all day long on ebay for 0.99p