custom ConfigMap coredns not working/persistent

I am making a custom configuration in the coredns configmap, however, after some time the file reverts back to the original and does not persist my settings! I saw that the config map has the following labels:

c3.doks.digitalocean.com/component=coredns
c3.doks.digitalocean.com/plane=data
doks.digitalocean.com/managed=true

Can anyone help me so that I can make my settings persistent?

Thanks