Bought a wrong Framemaker, needed a volume license

We work with a number of users with Adobe FrameMaker 12.

We get a new employee there and we need an additional license for version 12.

The latest version of frame maker however is 2015/2017.

I am informed by Adobe that it is possible to obtain a downgrade to version 12 for 1 license.

The order that i have placed for Framemaker 2015 trough my reseller now appears not to be a Framemaker volume license?

In order to downgrade the framemaker software i have to purchase the volume license of framemaker 2017.

My reseller says that he is not able to return the license of Framemaker 2015 that i have bought, because he already registrated it and returned it with a key license from Adobe. I have not used this key license. I want to return the wrong framemaker 2015 version and license and buy a volume license instead.

How can i arrange that?