TELECOMS NETWORK Energis has completed trials of the ultimate marketing bludgeon - unlimited access to free telephone calls funded by ads. Callers first dial a freephone number, followed by the number they want to reach. They are then greeted by an ad for anything from a local plumber to a national chainstore. The longer the call, the more ads assail the ear of the caller, although each commercial is preceded by a warning tone. The idea, which originated a year ago in Sweden, is likely to roll-out across the Energis national network in a few months.