Upgrade from Redhat 6 to Redhat 7

I've followed this https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Migration_Planning_Guide/chap-Red_Hat_Enterprise_Linux-Migration_Planning_Guide-Upgrading.html

When i did part 7 yum repolist it still list

rhel-6-server-rpms/7Server/x86_64 Red Hat Enterprise Linux 6 Server (RPMs) 0

How do I change it to list RHEL 7?