Hi a.jathar,
As Contract Renewal is based on your Licenses or Serial Number, you can have 2 resellers per Contract.
So if you currently have one Serial Number with multiple seats, you can just tell your current reseller that you are only renewing this/these number of seat/s for now. Once processed and they already provided you with an Autodesk Order Number, then you can renew the remaining seats with other resellers.
What will happen is that you will provided 2 different Renewal Numbers or Quote Numbers.
Hope this answers your question.
Joane Bonghanoy