Add a service line to a service contract from OM when the party is different

OK... here's the need.

We have a service contract for customer ABC. There 3rd party in the header of the Service contract is company XYZ. We are able to use XYZ Bill to info for the service contract lines.

We have a new Sales Order from company JKL, they place orders on behalf of their customers.

Is it possible to add a service line in OM for an install base instance owned by ABC and append it to the existing contract?

When we pull the available contracts from the LOV in the Service Details form in OM, the list does not contain the Service Contract for company ABC. We have tried creating a relationship in TCA, adding the party as 3rd party in the header of OKS and also even adding a relationship in Install Base for the instance. None of them seems to work.