Agencies - Yet Again

Registered with this agency in West London(Hounslow) and was informed that I'd be required to do evening work for one of their clients. I suppose I should have known better, sent them my availability dates and told them that I can work most afternoons into early evening as well. So far not even a dickie bird of a reply. Seems yet again that they either are so 'busy' that they haven't got the time to reply or just can't be bothered to reply as there is and never was any work. Me thinks its time to de register from them as well.