Many customers sign up for GitLab.com Subscription Plans and this guide will tell you how to verify what a customer has subscribed to.
Go to https://support-mw.gitlab.com/ and sign in with your GitLab Google Account
Once logged in, run a search for the customer (company or domain name)
If you find the result, click the arrow on the far right of the entry to see more
On this new page, you can find the plan and whether or not it is active.
Sign in to customers.gitlab.com using the support credentials in 1Password
Select Customers from the navigation on the left
In the Filter box, search for the customer using any of the criteria you got from the customer (name, company, etc.)
On the right side of the customer's entry, you will see a lowercase i. Click on it to see lots of this customer's data.
Sign in to Salesforce using the support credentials in 1Password
At the top of the page, search for the user or company
Look under the Accounts category for a result. Click on the Account Name that matches the company you're looking for.
Under GitLab Subscription Information look for the Purchased Products. You can also find the Next Renewal Date in this section.