You can normally transfer a domain away from Squarespace yourself by going to Settings, and then Domains. Select the domain to transfer and then uncheck Lock Domain. There's a full guide here: Transferring a domain away from Squarespace.
Note that you can only transfer a domain to another provider if it's been at least 60 days since it was registered or transferred to Squarespace. This is a restriction imposed by ICANN, not Squarespace.