bullseye?
check if /etc/unbound/unbound.conf.d/resolvconf_resolvers.conf, if it does, delete it and restart unbound. see here.
you also need to comment out the unbound entry in /etc/resolvconf.conf to prevent the config file (/etc/unbound/unbound.conf.d/resolvconf_resolvers.conf) to be recreated by resolvconf