Olga, have you checked out this
http://business.study.ru/lessons/start.php to begin with?
Why don`t you find courses with such program? I am sure conversational phone courses do not last more than a month and will be more useful. Besides, there are good videos of office English in bookshops. What do you want to get from these lessons? What should these phone lessons look like? Final question: where do you live?