Icloud storage plans

Hi, I've been on the icloud + storage basic plan for a while now that allows me 50GB of storage, so i've been paying for that each month.

I have recently joined my family sharing storage plan which give us 2TB of storage and I'm trying to cancel my old plan and stop paying for it since I'm on my family sharing plan. When i try to change it , it doesn't give me the option to cancel it....help please.