Hi,
Microsoft retired the “24×7 Problem Resolution Support” benefit under Software Assurance effective February 1, 2023.
https://www.microsoft.com/en-us/licensing/news/software-assurance-247support-retirement
New SA agreements no longer include technical support incidents. Software Assurance alone does not grant support—you must either have Unified or purchase incidents individually.
https://www.microsoft.com/en-us/microsoft-unified?activetab=pivot1%3aprimaryr8#areaheading-uid9cb3
As far as Service hub is concerned,you do not need a Unified Support contract to receive technical assistance. You can purchase support incidents through the Microsoft Services Hub (using a personal Microsoft account), and then apply them to corporate use.
About Service Hubs-
https://serviceshub.microsoft.com/home
Hope this helps!
Regards,
Shruti