Subscriptions changes - Defender for Business

Good morning, 

Any advice on how to convert subscriptions previously using E5 licenses and a combination of licenses to Defender for business? 
(The change subscription option is not present on the tenants)

Sitting with the following challenges:

1) I have one client using only Business premium licenses whose Security portal only reflects as per the screenshot below. How do I change this to Defender for Business?

2) I have another client using 4 * E5 licenses and 150 * Business Premium licenses. How do I change this to Defender for Business?

Any advice will be appreciated.