Complex sentence: Among 4 largest divisions of BT group are BT Retail, BT Wholesale, Openreach, and BT Global Services, each of which provides services to satisfy the needs of different customers-the individual, the small business or the multinational corporation.
Split into simpler sentences: Among 4 largest divisions of BT group are BT Retail, BT Wholesale, Openreach, and BT Global Services. With these 4 divisions, it provides services to satisfy the needs of diverse type of customers-the individual, the small business or the multinational corporation.