Most communication is done by logging into My Account and approving or rejecting your proofs.
If you reject your proofs, you can type out your concerns for the graphic folks who are working on your project.
If your order is open for corrections, (Incomplete) you can upload your new files and view an online digital proof before proceeding.
If you have general concerns over issues like resolution, our graphics team is going to do a prepress review prior to starting your project - https://support.discmakers.com/hc/en-us/articles/360033810174-What-Is-The-PrePress-Review - If they locate any areas for concern, they will notify you via email before moving into production.
You can also express any areas for concern with your product specialist. They can attach notes for the graphics team to review during this prepress review process.