Hi Chris,
There is a support guide that covers this scenario.
If you don't want to delegate admin permissions to the partner, they can contact Microsoft support and open a service request to renew the subscription.
"Customers can reassign or remove administrator permissions in a service's admin portal. However, unless you renegotiate your agreement with the customer, you continue to be responsible for providing customer support and adhering to the terms of the Cloud Reseller Agreement, even after a customer reassigns or removes administrator permissions. In this situation, if the customer requires help, you can call Microsoft support to open a service request on behalf of the customer."
Otherwise you can delegate access to the partner.