Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
You did not give enough details for us to understand your exact situation, so there may be a few possibilities -
Situation 1 - You purchased your direct licenses from the admin portal of your existing tenant
You were on a CSP licensing scheme purchasing from a reseller.
You went into admin portal of your tenant as global admin, and purchased licenses direct from Microsoft from within your tenant. In this case, you just need to go to each individual user and replace the CSP license with the one you purchased.
Situation 2 - You purchased your direct license outside of your existing tenant and in the process created another tenant.
Eg- assume old tenant is contoso.onmicrosoft.com
You were on a CSP licensing scheme purchasing from a reseller.
You DID NOT buy new licenses from within your tenant. Instead you purchased your licenses separately (eg going to https://www.microsoft.com/en-my/microsoft-365/business/microsoft-365-plans-and-pricing) and purchased with a fresh tenant (Eg- assume new tenant is contosonew.onmicrosoft.com) . In this case, these licenses cannot be retrospectively added to your old tenant. You will have to do a migration from your old tenant to this tenant. (Meaning you migrate from contoso.onmicrosoft.com to contosonew.onmicrosoft.com). Unfortunately, this is not a straight forward task, and not everything can be migrated. (eg Teams conversations would be problematic). Most companies engage a experienced Microsoft reseller/professional for this.
You also ask repeatedly on how to contact Microsoft. These are the ways
- Login to your M365 account as global admin and raise a support ticket or
- Phone https://support.microsoft.com/en-us/support/ - click Work Account
Hope this helps