Condolences on your loss.
If you can log into his account you can switch off membership plan auto-renewal and remove your registered card details so that no further membership renewals will be charged:
If you can't log into his account then contact 48 support and they should be able to assist you.
See the link in my signature below or email them at support@48months.zendesk.com
If there's any problem or delay in getting this sorted via 48 support then you may be able to stop any further card payments by contacting your bank.
