Hello Alex,
For enterprise agreement, please check with enterprise admin if the AO and DA view charges are enabled for the enrollment. If not please check with EA admin to follow the steps shared in the below document and have them enabled.
How to enable billing details for EA: https://learn.microsoft.com/en-us/azure/cost-management-billing/costs/assign-access-acm-data#enable-access-to-costs-in-the-ea-portal
With regards to RBAC who can view cost details are Enterprise admin, department admin, account owner ( based on the level of scope), contributor, cost management reader, cost management contributor roles.
However, AO and DA view charges should be enabled by EA Admin.
Hope this helps .
Kind regards
Divya.