Most DSL modems will work with other telco companies, you need to research the VPI/VCI that they use for the end customer. 99.9% run ATM from the Central Office to the customer. Where I live we use VPI of 8 and VCI of 35.
can't you change it's settings? through a web interface or something like that? if you can then you can prolly make that work with some other provider too... if you can't change settings, you can try overwriting the firmware and then applying some new settings... etc etc