A customer who has 24X7 support plan can call will get a phone number to call. This support plan is typically done for on prem deployments or for hosted compliance and security deployments . It does not apply to Channel management customers by default.
Using the AGAT support phones is limited to customers with a 24X7 SMP and for critical issues, that is, issues with a critical business impact, meaning those entailing a significant commercial loss or degradation of services.
At any case, when contacting AGAT by phone, it is mandatory that you send, in parallel, an email containing all logs and details.