How to add extra functionality to an existing method class dynamically with DI?

I am looking for the best pattern to apply in my problem. I have an interface that defines my service class functionality

interface NegotiationInterface {
    abstract public function resetNegotiation(Negotiation $negotiantion);
} 

A main class implements it

public class NegotiationService implements NegotiationInterface {

    public function __construct(…Some Dependencies…)
    {
    ….        
    }

    public function resetNegotiation(Negotiation $negotiantion){
    …. //All business logic
    }
}

NegotiationService is registered under DI container(Symfony based) and used all over application by its service id.

$negotiationService = $this->container->get(“negotiation_service”);
$negotiationService->resetNegotiation($negotiation);

However some of our clients(negotiation contains the client info), require an additional step after calling resetNegotiation, for example our common business logic + calling a webservice. I reached at decorator pattern but I am not sure if it would be the best approach while using DI. If so how would I apply together with DI. I would like to have those extra steps loaded dynamically according to client.