Dedicated short range communication (DSRC) has been allocated (3 EU, 7 US) dedicated channels at 5.9GHz for vehicular communications. Although resource allocations on the Control Channel (CCH) reserved for safety-related applications have been well investigated, efficient usage of the other Service Channels (SCH) has attracted less attention. In this paper, we propose the design of an asynchronous multichannel mechanism for service management at 5.9GHz. Whereas the service phase defined in the IEEE WAVE standard requires vehicles to remain tuned on a given service channel, the proposed mechanism relies on cognitive principles to let service providers and users dynamically switch between channels and converge to a rendezvous channel where they can negotiate service support and conditions. The mechanism has been implemented on the ETSI compliant ITS simulation platform iTETRIS. We investigate the delay required to converge to such rendezvous channel and illustrate that an optimal cognitive parameter set manages to keep it within an acceptable range, and yet provides more flexibility to the channel usage.