Being Charged for something I don't want

I am being charged for a service I don't want, but I can't cancel on thier website because I can't login.  They won't recognize my e-mail and I always use the same password.  They wont let me cancel without logging in and don't provide an 800 number.  I'm going to my bank tomorrow, but I'm not sure what they can do and I'm angry tonight after reading my last statement.  This has got to end.