Ring the council and explain the situation to them. If your name is on the tenancy, you'll have to pay it. You can argue that you should only pay the rate that single people living alone pay though to get a discount due to living with exempt people. When I lived in barnsley I was classed as a full time student (placement year) so didn't have to pay, but my gf at the time was liable for it as she wasnt a student. She got a 25% discount though due to my exemption.