A Veeam Cloud Service Provider is only permitted to assign the Case Administrator role to employees and contractors working on behalf of the Service Provider.
As documented within the Veeam Cloud Service Provider Program Guide:
Deployments can be either single tenant or multi-tenant and there is no specific requirement on types of services that must be offered, with exception of [the VCSP partner] providing product support to [their] end customers.
VCSP licensing is intended to equip the VCSP partner to deliver hosting, cloud or managed services to its customer(s). VCSP licensing is not intended as an alternative to Veeam end customer licenses or as a way for customers to use Veeam products on a monthly basis.
As part of their relationship with Veeam, VCSP partners are afforded access to certain benefits — such as technical support and certain promotional offers — that are not extended to VCSP customers.
This means that a VCSP Partner is not allowed to assign their customer(s) as a Case Administrator. The Technical Support contract associated with the VCSP Partner's licenses only entitles the VCSP Partner themself access to Veeam Support.