Don't you think the COs know that the applicants on ALL their cases are waiting for news?
I always say, if your reason for calling comes down to only, 'I am here, waiting - tell me something,' then don't call. The CO WILL contact you if they have anything to tell you, or they need more information. Otherwise, it's polite to let them get on with their job. INZ has a strictly enforced routine of date-order working, so no amount of calls asking for updates are going to have the effect of prodding a CO to deal with that person's case more quickly, and in any case, a lot of the verification depends on getting answers from third parties, so if they haven't yet supplied those answers, there is nothing the CO can do but wait, until they have been able to tick off all the requirements.