What exactly do you mean by "cancel membership/plan"?
You can't cancel a membership plan once it has started.
If it's a stacked upcoming membership plan on your account that hasn't started yet and you are looking for a refund then you'll have to contact 48 support to ask them if they can help.
If you mean that you want to leave 48 and move to another provider then see here:
If your issue is something else then you'll need to explain it in more detail and more clearly.
If you need to contact 48 support about this then see the links in my signature below.
