There is no problem to change the CNAME records for your domain. Eicra.com customers can request this service from:
Login to http://billing.eicra.com by using username and password.
Customers' Area --> My Domains --> Click Active icon on the rightmost of each domains --> Manage DNS
You should post a general ticket there about CNAME records you would like to give you guidance on how you can put your CNAME. We always recommend you to consult with a DNS expert regarding this issue.
You can sign up for a hosting account with Eicra.com and let us take care of your domain's DNS records for you.