It's not as easy as that. Some work is required to activate your BT Openreach line at the exchange. Also Now Broadband and phone uses the Sky voice and broadband network, its an LLU product.
It's really down to BT and what work needs to be done. If the line has been completely disconnected, this will take some time.
LLU stands for local loop unbundling, the local loop is the line between your home and BT's exchange. Unbundling means that at the exchange Sky have enabled there own software to carry Internet and phone calls.