help for password of 186 box

i m using sisco 186 box and its version is Version: v3.1.0 atasip (Build 040211A)
now my problem is i gave my sisco to one calling card company to configure my cisco for their service now they had put password on my sisco and not telling me that password. i need that password cos i have to switch my sisco from cable to dialup through isdn router

so plz any body help me out that how can i find their password
and if i use FACTRESET# method it will reset my sisco so i wont be able to use their service

so is ther any intelligent guy or gal out ther who can help me

waiting for some favourable reply