Thanks!Buy or borrow cheap used router (like an old Linksys wrt3g one)
Power it on (does not have to be connected to the internet) and make sure it's on a different subnet than the real router you use so it doesn't interfere (i.e. switch it to 192.168.2.1 if your normal router is on 192.168.1.0/8)
Connect your phone to it
Connect your pc to it
Use telnet as stated in the OP
Either that or reset your current router back to factory defaults and regain the login password.