If you are using ns-743.awsdns-28.net
, ns-1077.awsdns-06.org
, ns-246.awsdns-30.com
, or ns-2021.awsdns-60.co.uk
as your nameservers then you "ARE" using Route 53 at some point along the way.
If you are sure those nameserver values are accurate, you'll need to figure out which AWS account is handling those records and edit them in Route 53 because that's where the actual host records will live.
Alternatively, if you want to configure your CNAME, A, etc records in your "other provider", then you'll need to remove those "nameserver" records that point to Route 53 (awsdns) and configure them appropriately for that provider. You can ask the provider (or refer to their docs) for what the default nameserver values are supposed to be.
For example, if you're using Namecheap, you can search Google for "namecheap default nameservers" to find the info without having to contact Namecheap. Do that for whatever your provider actually is. Sometimes you don't even need to know the values and you can just revert to the default in the provider configuration (which will wipe out custom settings).