connecting to Internet with my BT HH3 with different ISP

Hi there, im most probably flogging a dead horse but I Bought a BT Home Hub 3 last year at a car boot sale and I would love to put it in use now. Have found by entering /thd_setup and put in the vci/pci and changed adsl to PPPOE and ive actually got it locked onto the DSL signal, all that part is working fine. but I just cannot connect to the internet with it - my isp username is so i over-right the bt username and i put my password in and a message says something about username not allowed or something like that, even when i do it through 'setup for other isp' in settings it wont accept them and connect onto the internet even though i have the DSL trained and locked. anything else i can try or shall i just give up now? - many thanks.