DNTServicesPlus.com was already added to a different Office 365 tenant NETORGFT2144743.onmicrosoft.com which is managed by GoDaddy. To add this domain to this tenant you will need to contact GoDaddy support and have this domain removed from NETORGFT2144743.onmicrosoft.com. Once done you can come back and resume this step.
Based on the provided error message, it sounds like that domain is already setup on a Office 365 email account and is with us. I suggest contacting our support team and they can assist you with your options to get the correct email address setup.